diff --git a/doc/environments/groupthm/groupthm.dtx b/doc/environments/groupthm/groupthm.dtx
index 3c39495..1593ede 100644
--- a/doc/environments/groupthm/groupthm.dtx
+++ b/doc/environments/groupthm/groupthm.dtx
@@ -843,22 +843,21 @@
 %    \begin{macrocode}
 \RequirePackage{amsthm}
 \RequirePackage{thmtools}
-\RequirePackage{mkessler-powerset}
 %    \end{macrocode}
 %
-% \begin{macro}{\@@_declare_theorem_group:nn, \@@_declare_theorem_group:nV}
+% \begin{macro}{\@@_thmtools_declare_theorem:nn, \@@_thmtools_declare_theorem:Vn}
 %   \begin{syntax}
-%     \cs{@@_declare_theorem_group:nn} \meta{theorem name}\meta{thmtools keyval args}
+%     \cs{@@_thmtools_declare_theorem:nn} \meta{theorem name}\meta{thmtools keyval args}
 %   \end{syntax}
 % 
 %  This is just a private wrapper around \cs{declaretheorem} of the \pkg{thmtools} package.
 % 
 %    \begin{macrocode}
-\cs_new:Npn \@@_declare_theorem_group:nn #1 #2
+\cs_new:Npn \@@_thmtools_declare_theorem:nn #1 #2
 {
-  \declaretheorem [ #2 ] { #1 }
+  \declaretheorem [ #1 ] { #2 }
 }
-\cs_generate_variant:Nn \@@_declare_theorem_group:nn { n V }
+\cs_generate_variant:Nn \@@_thmtools_declare_theorem:nn { V n }
 %    \end{macrocode}
 % \end{macro}
 %
@@ -1788,13 +1787,13 @@
 % Finally, apply the additional \pkg{thmtools} keys for this specific theorem.
 % Putting them last will overwrite keys that were given by the groups.
 %    \begin{macrocode}
-    \clist_put_right:n \l_@@_thmtools_clist { #4 }
+    \clist_put_right:Nn \l_@@_thmtools_clist { #4 }
 %    \end{macrocode}
 % We can now pass our list to \pkg{thmtools}, declaring the theorem.
 %    \begin{macrocode}
-    \@@_declare_theorem:nV
-      { #1 }
+    \@@_thmtools_declare_theorem:Vn
       \l_@@_thmtools_clist
+      { #1 }
   }
 %    \end{macrocode}
 % \end{macro}
@@ -1806,7 +1805,7 @@
 % 
 % 
 %
-% \begin{macro}{\groupthm_new_grouped_theorem:nnnn}
+% \begin{macro}{\groupthm_new_grouped_theorem:nnnn,\groupthm_new_grouped_theorem:nVVV}
 %    \begin{syntax}
 %       \cs{groupthm_new_grouped_theorem:nnnn}\ma{environment name}
 %       \ma{groups clist}\ma{theorem name}\ma{thmtools keys}
@@ -1822,19 +1821,20 @@
 %    \begin{macrocode}
     \cs_if_exist:cTF { #1 }
       {
-        \msg_error:{ groupthm } { wrong ~ definition }
+        \msg_error:nnnnn { groupthm } { wrong ~ definition }
           { grouped ~ theorem } { #1 } { already }
       }
       {
-        \@@_groupthm_declare_grouped_theorem_aux:nnnn
+        \@@_declare_grouped_theorem_aux:nnnn
           { #1 } { #2 } { #3 } { #4 }
       }
   }
+\cs_generate_variant:Nn \groupthm_new_grouped_theorem:nnnn { n V V V }
 %    \end{macrocode}
 % \end{macro}
 % 
 % 
-% \begin{macro}{\groupthm_provide_grouped_theorem:nnnn}
+% \begin{macro}{\groupthm_provide_grouped_theorem:nnnn,\groupthm_provide_grouped_theorem:nVVV}
 %		 
 %    \begin{macrocode}
 \cs_new:Npn \groupthm_provide_grouped_theorem:nnnn #1 #2 #3 #4
@@ -1846,10 +1846,11 @@
 %    \begin{macrocode}
     \cs_if_exist:cF { #1 }
       {
-        \@@_groupthm_declare_grouped_theorem_aux:nnnn
+        \@@_declare_grouped_theorem_aux:nnnn
           { #1 } { #2 } { #3 } { #4 }
       }
   }
+\cs_generate_variant:Nn \groupthm_provide_grouped_theorem:nnnn { n V V V }
 %    \end{macrocode}
 % \end{macro}
 % 
@@ -1893,7 +1894,7 @@
 % 
 % 
 % 
-% \begin{macro}{\groupthm_new_theorem:nnnn}
+% \begin{macro}{\groupthm_new_theorem:nnnn,\groupthm_new_theorem:nVVV}
 %    \begin{syntax}
 %       \cs{groupthm_new_theorem:nnnn}\ma{environment name}
 %       \ma{groups clist}\ma{theorem name}\ma{thmtools keys}
@@ -1908,12 +1909,13 @@
     \groupthm_new_grouped_theorem:nnnn
       { #1* } { #2, starred } { #3 } { #4 }
   }
+\cs_generate_variant:Nn \groupthm_new_theorem:nnnn { n V V V }
 %    \end{macrocode}
 % \end{macro}
 % 
 % 
 % 
-% \begin{macro}{\groupthm_provide_theorem:nnnn}
+% \begin{macro}{\groupthm_provide_theorem:nnnn,\groupthm_provide_theorem:nVVV}
 %    \begin{syntax}
 %       \cs{groupthm_provide_theorem:nnnn}\ma{environment name}
 %       \ma{groups clist}\ma{theorem name}\ma{thmtools keys}
@@ -1928,6 +1930,7 @@
     \groupthm_provide_grouped_theorem:nnnn
       { #1* } { #2, starred } { #3 } { #4 }
   }
+\cs_generate_variant:Nn \groupthm_provide_theorem:nnnn { n V V V }
 %    \end{macrocode}
 % \end{macro}
 % 
@@ -1979,7 +1982,7 @@
 %    \begin{macrocode}
 \cs_new:Npn \groupthm_new_grouped_theorem_from_keys:nn #1 #2
   {
-    \@@_set_normalized_keys { #2 } { groupedtheorem } { #1 }
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
 
     \groupthm_new_grouped_theorem:nVVV
       { #1 }
@@ -1995,7 +1998,7 @@
 %    \begin{macrocode}
 \cs_new:Npn \groupthm_provide_grouped_theorem_from_keys:nn #1 #2
   {
-    \@@_set_normalized_keys { #2 } { groupedtheorem } { #1 }
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
 
     \groupthm_provide_grouped_theorem:nVVV
       { #1 }
@@ -2011,10 +2014,10 @@
 %    \begin{macrocode}
 \cs_new:Npn \groupthm_new_grouped_theorem_star_from_keys:nn #1 #2
   {
-    \@@_set_normalized_keys { #2 } { groupedtheorem } { #1 }
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
 
     \groupthm_new_grouped_theorem_star:nVVV
-      { #1 }
+      { #2 }
       \l_@@_key_group_clist
       \l_@@_name_tl
       \l_@@_key_thmtools_clist
@@ -2027,10 +2030,10 @@
 %    \begin{macrocode}
 \cs_new:Npn \groupthm_provide_grouped_theorem_star_from_keys:nn #1 #2
   {
-    \@@_set_normalized_keys { #2 } { groupedtheorem } { #1 }
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
 
     \groupthm_provide_grouped_theorem_star:nVVV
-      { #1 }
+      { #2 }
       \l_@@_key_group_clist
       \l_@@_name_tl
       \l_@@_key_thmtools_clist
@@ -2044,10 +2047,10 @@
 %    \begin{macrocode}
 \cs_new:Npn \groupthm_new_theorem_from_keys:nn #1 #2
   {
-    \@@_set_normalized_keys { #2 } { groupedtheorem } { #1 }
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
 
     \groupthm_new_theorem:nVVV
-      { #1 }
+      { #2 }
       \l_@@_key_group_clist
       \l_@@_name_tl
       \l_@@_key_thmtools_clist
@@ -2060,10 +2063,10 @@
 %    \begin{macrocode}
 \cs_new:Npn \groupthm_provide_theorem_from_keys:nn #1 #2
   {
-    \@@_set_normalized_keys { #2 } { groupedtheorem } { #1 }
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
 
     \groupthm_provide_theorem:nVVV
-      { #1 }
+      { #2 }
       \l_@@_key_group_clist
       \l_@@_name_tl
       \l_@@_key_thmtools_clist
@@ -2076,7 +2079,7 @@
 %    \begin{macrocode}
 \cs_new:Npn \groupthm_new_theorem_star_from_keys:nn #1 #2
   {
-    \@@_set_normalized_keys { #2 } { groupedtheorem } { #1 }
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
 
     \groupthm_new_theorem_star:nVVV
       { #1 }
@@ -2092,7 +2095,7 @@
 %    \begin{macrocode}
 \cs_new:Npn \groupthm_provide_theorem_star_from_keys:nn #1 #2
   {
-    \@@_set_normalized_keys { #2 } { groupedtheorem } { #1 }
+    \@@_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
 
     \groupthm_provide_theorem_star:nVVV
       { #1 }
diff --git a/doc/environments/groupthm/groupthm.sty b/doc/environments/groupthm/groupthm.sty
new file mode 100644
index 0000000..a0cf7c4
--- /dev/null
+++ b/doc/environments/groupthm/groupthm.sty
@@ -0,0 +1,584 @@
+%%
+%% This is file `groupthm.sty',
+%% generated with the docstrip utility.
+%%
+%% The original source files were:
+%%
+%% groupthm.dtx  (with options: `package')
+%% 
+%% IMPORTANT NOTICE:
+%% 
+%% For the copyright see the source file.
+%% 
+%% Any modified versions of this file must be renamed
+%% with new filenames distinct from groupthm.sty.
+%% 
+%% For distribution of the original source see the terms
+%% for copying and modification in the file groupthm.dtx.
+%% 
+%% This generated file may be distributed as long as the
+%% original source files, as listed above, are part of the
+%% same distribution. (The sources need not necessarily be
+%% in the same archive or directory.)
+%% File: groupthm.dtx
+\ProvidesExplPackage{groupthm}{2022/01/17}{0.0.1}{Grouped theorems.}
+\RequirePackage{amsthm}
+\RequirePackage{thmtools}
+\cs_new:Npn \__groupthm_thmtools_declare_theorem:nn #1 #2
+{
+  \declaretheorem [ #1 ] { #2 }
+}
+\cs_generate_variant:Nn \__groupthm_thmtools_declare_theorem:nn { V n }
+\cs_new:Npn \__groupthm_hook_gset_rule_foreach:nNnn #1 #2 #3 #4
+  {
+    \cs_set:Npn \__groupthm_map_aux:n ##1
+    {
+      \hook_gset_rule:nnnn { #1 } { ##1 } { #3 } { #4 }
+    }
+    \clist_map_function:NN #2 \__groupthm_map_aux:n
+  }
+\msg_new:nnn { groupthm } { unknown ~ group }
+{
+  Unknown  ~ group ~ '#1' ~ supplied ~ \msg_line_context:
+}
+\msg_new:nnn { groupthm } { unknown ~ key }
+{
+  Unknown ~  key ~ '#1' ~ supplied ~ \msg_line_context:
+}
+\msg_new:nnn { groupthm } { wrong ~ definition }
+{
+  Bad ~ definition ~ of ~ #1 ~ '#2' ~ \msg_line_context:, ~ #1 ~ is ~ #3 ~ defined.
+}
+\hook_new:n { __groupthm/prename   }
+\hook_new:n { __groupthm/postname  }
+\hook_new:n { __groupthm/mapname   }
+\hook_new:n { __groupthm/thmtools  }
+\hook_new:n { __groupthm/groupsort }
+\cs_generate_variant:Nn \hook_gset_rule:nnnn { n n V n }
+\tl_new:N    \l__groupthm_key_prename_tl
+\tl_new:N    \l__groupthm_key_name_tl
+\tl_new:N    \l__groupthm_key_postname_tl
+\clist_new:N \l__groupthm_key_group_clist
+\clist_new:N \l__groupthm_key_mapname_clist
+\clist_new:N \l__groupthm_key_thmtools_clist
+\tl_new:N    \l__groupthm_prename_tl
+\tl_new:N    \l__groupthm_name_tl
+\tl_new:N    \l__groupthm_postname_tl
+\clist_new:N \l__groupthm_mapname_clist
+\clist_new:N \l__groupthm_thmtools_clist
+\clist_new:N \l__groupthm_group_clist
+\clist_new:N \g__groupthm_defined_theorem_groups_clist
+\keys_define:nn { groupthm }
+  {
+    prename      .tl_set:N      = \l__groupthm_key_prename_tl,
+    prename      .default:n     = \c_empty_tl,
+    prename      .groups:n      = { theoremgroup },
+    name         .tl_set:N      = \l__groupthm_key_name_tl,
+    name         .default:n     = \c_novalue_tl,
+    name         .groups:n      = { groupedtheorem, theoremvariants },
+    postname     .tl_set:N      = \l__groupthm_key_postname_tl,
+    postname     .default:n     = \c_empty_tl,
+    postname     .groups:n      = { theoremgroup },
+    group        .clist_set:N   = \l__groupthm_key_group_clist,
+    group        .default:n     = {},
+    group        .groups:n      = { groupedtheorem, theoremvariants },
+    mapname      .clist_set:N   = \l__groupthm_mapname_clist,
+    mapname      .default:n     = {},
+    mapname      .groups:n      = { theoremgroup },
+    thmtools     .clist_set:N   = \l__groupthm_key_thmtools_clist,
+    thmtools     .default:n     = {},
+    thmtools     .groups:n      =
+      { theoremgroup, groupedtheorem, theoremvariants },
+    unknown      .code:n        =
+      \msg_error:nnn { groupthm } { unknown ~ group } { \l_keys_key_str }
+  }
+\cs_new:Npn \__groupthm_set_normalized_keys:nnn #1 #2 #3
+  {
+    \keys_set:nn { groupthm } { prename, name, postname, group, mapname, thmtools }
+    \keys_set_groups:nnn { groupthm } { #2 } { #1 }
+    \tl_if_eq:NnTF \l__groupthm_key_name_tl { \c_novalue_tl }
+      {
+        \tl_set:Nx \l__groupthm_name_tl
+          {
+            \text_titlecase_first:n {#3}
+          }
+      }
+      {
+        \tl_set_eq:NN \l__groupthm_name_tl \l__groupthm_key_name_tl
+      }
+    \tl_set_eq:NN    \l__groupthm_prename_tl     \l__groupthm_key_prename_tl
+    \tl_set_eq:NN    \l__groupthm_postname_tl    \l__groupthm_key_postname_tl
+    \clist_set_eq:NN \l__groupthm_group_clist    \l__groupthm_key_group_clist
+    \clist_set_eq:NN \l__groupthm_mapname_clist  \l__groupthm_key_mapname_clist
+    \clist_set_eq:NN \l__groupthm_thmtools_clist \l__groupthm_key_thmtools_clist
+  }
+\cs_new:Npn \__groupthm_add_to_theorem_group_ordering:n #1
+  {
+    \__groupthm_hook_gset_rule_foreach:nNnn
+      { __groupthm/groupsort }
+      \g__groupthm_defined_theorem_groups_clist
+      { before }
+      { #1 }
+  }
+\cs_new:Npn \__groupthm_remove_from_theorem_group_ordering:n #1
+  {
+    \__groupthm_hook_gset_rule_foreach:nNnn
+      { __groupthm/groupsort }
+      \g__groupthm_defined_theorem_groups_clist
+      { unrelated }
+      { #1 }
+  }
+\cs_new:Npn \__groupthm_add_to_sort_hook:n #1
+{
+  \hook_gput_code:nnn { __groupthm/groupsort }
+  { #1 }
+  {
+    \clist_put_left:Nn \l__groupthm_group_clist { #1 }
+  }
+}
+\cs_new:Npn \__groupthm_sort_theorem_group_names:
+  {
+    \hook_gremove_code:nn { __groupthm/groupsort  }{*}
+    \clist_map_function:NN \l__groupthm_group_clist \__add_to_sort_hook:n
+    \clist_clear:N \l__groupthm_group_clist
+    \hook_use:n { __groupthm/groupsort }
+  }
+\cs_new:Npn \__groupthm_declare_theorem_group_aux:nnnnn #1#2#3#4#5
+  {
+  \cs_new:cpn { __groupthm_use_group_#1: }
+    {
+      \hook_gput_code:nnn { __groupthm/prename } { #1 }
+        {
+            \tl_put_left:Nx \l__groupthm_prename_tl { #2 }
+        }
+      \hook_gput_code:nnn { __groupthm/postname } { #1 }
+        {
+            \tl_put_right:Nx \l__groupthm_postname_tl { #3 }
+        }
+      \hook_gput_code:nnn { __groupthm/mapname } { #1 }
+        {
+          \clist_put_right:Nn \l__groupthm_mapname_clist { #4 }
+        }
+      \hook_gput_code:nnn { __groupthm/thmtools } { #1 }
+        {
+          \clist_put_right:Nn \l__groupthm_thmtools_clist { #5 }
+        }
+    }
+    \__groupthm_add_to_theorem_group_ordering:n { #1 }
+    \clist_gput_left:Nn \g__groupthm_defined_theorem_groups_clist { #1 }
+  }
+\cs_new:Npn \__groupthm_undeclare_theorem_group_aux:n #1
+  {
+    \cs_undefine:c { __groupthm_use_group_#1:   }
+    \hook_gremove_code:nn { __groupthm/prename  } { #1 }
+    \hook_gremove_code:nn { __groupthm/postname } { #1 }
+    \hook_gremove_code:nn { __groupthm/mapname  } { #1 }
+    \hook_gremove_code:nn { __groupthm/thmtools } { #1 }
+    \clist_gremove_all:Nn  \g__groupthm_defined_theorem_groups_clist { #1 }
+    \__groupthm_hook_gset_rule_foreach:nNnn
+      { ?? }
+      \g__groupthm_defined_theorem_groups_clist
+      { unrelated }
+      { #1 }
+    \__groupthm_hook_gset_rule_foreach:nNnn
+      { __groupthm/prename }
+      \g__groupthm_defined_theorem_groups_clist
+      { unrelated }
+      { #1 }
+    \__groupthm_hook_gset_rule_foreach:nNnn
+      { __groupthm/postname }
+      \g__groupthm_defined_theorem_groups_clist
+      { unrelated }
+      { #1 }
+    \__groupthm_hook_gset_rule_foreach:nNnn
+      { __groupthm/mapname }
+      \g__groupthm_defined_theorem_groups_clist
+      { unrelated }
+      { #1 }
+    \__groupthm_hook_gset_rule_foreach:nNnn
+      { __groupthm/thmtools }
+      \g__groupthm_defined_theorem_groups_clist
+      { unrelated }
+      { #1 }
+    \__groupthm_remove_from_theorem_group_ordering:n { #1 }
+  }
+\cs_new:Npn \groupthm_new_theorem_group:nnnnn #1 #2 #3 #4 #5
+  {
+    \cs_if_exist:cTF { __groupthm_use_group_#1: }
+      {
+        \msg_error:nnnnn { groupthm } { wrong ~ definition }
+          { theorem ~ group } { #1 } { already }
+      }
+      {
+        \__groupthm_declare_theorem_group_aux:nnnnn { #1 } { #2 } { #3 } { #4 } { #5 }
+      }
+  }
+\cs_generate_variant:Nn \groupthm_new_theorem_group:nnnnn { n V V V V }
+\cs_new:Npn \groupthm_renew_theorem_group:nnnnn #1 #2 #3 #4 #5
+  {
+    \cs_if_exist:cTF { __groupthm_use_group_#1: }
+      {
+        \__groupthm_undeclare_theorem_group_aux:n { #1 }
+        \__groupthm_declare_theorem_group_aux:nnnnn { #1 } { #2 } { #3 } { #4 } { #5 }
+      }
+      {
+        \msg_error:nnnnn { groupthm } { wrong ~ definition }
+          { theorem ~ group } { #1 } { not }
+      }
+  }
+\cs_generate_variant:Nn \groupthm_renew_theorem_group:nnnnn { n V V V V }
+\cs_new:Npn \groupthm_provide_theorem_group:nnnnn #1 #2 #3 #4 #5
+  {
+    \cs_if_exist:cF { __groupthm_use_group_#1: }
+      {
+        \__groupthm_declare_theorem_group_aux:nnnnn { #1 } { #2 } { #3 } { #4 } { #5 }
+      }
+  }
+\cs_generate_variant:Nn \groupthm_provide_theorem_group:nnnnn { n V V V V }
+\cs_new:Npn \groupthm_declare_theorem_group:nnnnn #1 #2 #3 #4 #5
+  {
+    \cs_if_exist:cT { __groupthm_use_group_#1: }
+      {
+        \__groupthm_undeclare_theorem_group_aux:n { #1 }
+      }
+      \__groupthm_declare_theorem_group_aux:nnnnn { #1 } { #2 } { #3 } { #4 } { #5 }
+  }
+\cs_generate_variant:Nn \groupthm_declare_theorem_group:nnnnn { n V V V V }
+\cs_new:Npn \groupthm_new_theorem_group_from_keys:nn #1#2
+{
+  \__groupthm_set_normalized_keys:nnn { #1 } { theoremgroup } { #2 }
+  \groupthm_new_theorem_group:nVVVV { #2 }
+    \l__groupthm_prename_tl
+    \l__groupthm_postname_tl
+    \l__groupthm_mapname_clist
+    \l__groupthm_thmtools_clist
+}
+\cs_new:Npn \groupthm_renew_theorem_group_from_keys:nn #1#2
+{
+  \__groupthm_set_normalized_keys:nnn { #1 } { theoremgroup } { #2 }
+  \groupthm_renew_theorem_group:nVVVV { #2 }
+    \l__groupthm_prename_tl
+    \l__groupthm_postname_tl
+    \l__groupthm_mapname_clist
+    \l__groupthm_thmtools_clist
+}
+\cs_new:Npn \groupthm_provide_theorem_group_from_keys:nn #1#2
+{
+  \__groupthm_set_normalized_keys:nnn { #1 } { theoremgroup } { #2 }
+  \groupthm_provide_theorem_group:nVVVV { #2 }
+    \l__groupthm_prename_tl
+    \l__groupthm_postname_tl
+    \l__groupthm_mapname_clist
+    \l__groupthm_thmtools_clist
+}
+\cs_new:Npn \groupthm_declare_theorem_group_from_keys:nn #1#2
+{
+  \__groupthm_set_normalized_keys:nnn { #1 } { theoremgroup } { #2 }
+  \groupthm_declare_theorem_group:nVVVV { #2 }
+    \l__groupthm_prename_tl
+    \l__groupthm_postname_tl
+    \l__groupthm_mapname_clist
+    \l__groupthm_thmtools_clist
+}
+\NewDocumentCommand{\NewTheoremGroup}{ O{} m }
+  {
+    \groupthm_new_theorem_group_from_keys:nn { #1 } { #2 }
+  }
+\NewDocumentCommand{\RenewTheoremGroup}{ O{} m }
+  {
+    \groupthm_renew_theorem_group_from_keys:nn { #1 } { #2 }
+  }
+\NewDocumentCommand{\ProvideTheoremGroup}{ O{} m }
+  {
+    \groupthm_provide_theorem_group_from_keys:nn { #1 } { #2 }
+  }
+\NewDocumentCommand{\DeclareTheoremGroup}{ O{} m }
+  {
+    \groupthm_declare_theorem_group_from_keys:nn { #1 } { #2 }
+  }
+\cs_new:Npn \groupthm_declare_theorem_group_rule:nnnn #1 #2 #3 #4
+  {
+    \str_set:Nx \l_tmpa_str { \tl_trim_spaces:n { #3 } }
+
+    \str_if_eq:VnT \l_tmpa_str { higher }
+    {
+      \str_set:Nn \l_tmpa_tl { after }
+    }
+
+    \str_if_eq:VnT \l_tmpa_str { lower }
+    {
+      \str_set:Nn \l_tmpa_tl { before }
+    }
+
+    \str_if_eq:nnTF { #1 } { ?? }
+    {
+      \hook_gset_rule:nnVn {??} {#2} \l_tmpa_tl {#4}
+    }
+    {
+      \hook_gset_rule:nnVn { __groupthm / #1 } {#2} \l_tmpa_tl {#4}
+    }
+  }
+
+\NewDocumentCommand { \DeclareTheoremGroupRule } { O{??} m m m }
+  {
+    \groupthm_declare_theorem_group_rule:nnnn {#1} {#2} {#3} {#4}
+  }
+  % \subsection{Iterating over powersets}
+\clist_new:N  \l__powerset_copied_clist
+\seq_new:N    \l__powerset_saved_seq
+\cs_generate_variant:Nn \clist_remove_all:Nn { N V }
+\cs_new:Npn \__powerset_clist_foreach_aux:Nn #1 #2
+  {
+    \clist_if_empty:NTF \l__powerset_copied_clist
+      {
+        #2
+      }
+      {
+        \clist_get:NN \l__powerset_copied_clist \l_tmpa_tl
+        \seq_push:NV  \l__powerset_saved_seq \l_tmpa_tl
+        \clist_pop:NN \l__powerset_copied_clist { \l_tmpa_tl }
+
+        \__powerset_clist_foreach_aux:Nn #1 {#2}
+
+        \seq_get:NN \l__powerset_saved_seq \l_tmpa_tl
+        \clist_put_left:NV #1 \l_tmpa_tl
+
+        \__powerset_clist_foreach_aux:Nn #1 {#2}
+
+        \seq_get:NN \l__powerset_saved_seq \l_tmpa_tl
+        \clist_remove_all:NV #1 \l_tmpa_tl
+        \clist_push:NV \l__powerset_copied_clist \l_tmpa_tl
+        \seq_pop:NN \l__powerset_saved_seq \l_tmpa_tl
+      }
+  }
+\cs_new:Npn \powerset_clist_foreach:Nn #1 #2
+  {
+    \clist_set_eq:NN \l__powerset_copied_clist #1
+    \clist_clear:N #1
+    \clist_remove_duplicates:N \l__powerset_copied_clist
+    \__powerset_clist_foreach_aux:Nn #1 {#2}
+    \clist_set_eq:NN #1 \l__powerset_copied_clist
+  }
+\cs_new:Npn \__groupthm_use_theorem_group:n #1
+  {
+    \cs_if_exist_use:cF { __groupthm_use_group_#1: }
+    {
+      \msg_error:nnn { groupthm } { unknown ~ group } { #1 }
+    }
+  }
+\cs_new:Npn \__groupthm_use_function_on_name:n #1
+  {
+    \tl_set:Nx \l__groupthm_name_tl
+      {
+        #1 { \tl_use:N \l__groupthm_name_tl }
+      }
+  }
+\cs_new:Npn \__groupthm_declare_grouped_theorem_aux:nnnn #1 #2 #3 #4
+  {
+    \tl_clear:N     \l__groupthm_prename_tl
+    \tl_set:Nn      \l__groupthm_name_tl        { #3 }
+    \tl_clear:N     \l__groupthm_postname_tl
+    \clist_clear:N  \l__groupthm_mapname_clist
+    \clist_clear:N  \l__groupthm_thmtools_clist
+    \hook_gremove_code:nn { __groupthm/prename  }{*}
+    \hook_gremove_code:nn { __groupthm/postname }{*}
+    \hook_gremove_code:nn { __groupthm/mapname  }{*}
+    \hook_gremove_code:nn { __groupthm/thmtools }{*}
+    \clist_map_function:nN { #2 } \__groupthm_use_theorem_group:n
+    \hook_use:n { __groupthm/prename }
+    \hook_use:n { __groupthm/postname }
+    \hook_use:n { __groupthm/mapname }
+    \hook_use:n { __groupthm/thmtools }
+    \clist_map_function:NN \l__groupthm_mapname_clist \map_use_on_name:n
+    \clist_put_right:Nx \l__groupthm_thmtools_clist
+      {
+        name = \tl_use:N \l__groupthm_prename_tl
+               \tl_use:N \l__groupthm_name_tl
+               \tl_use:N \l__groupthm_postname_tl
+      }
+    \clist_put_right:Nn \l__groupthm_thmtools_clist { #4 }
+    \__groupthm_thmtools_declare_theorem:Vn
+      \l__groupthm_thmtools_clist
+      { #1 }
+  }
+\cs_new:Npn \groupthm_new_grouped_theorem:nnnn #1 #2 #3 #4
+  {
+    \cs_if_exist:cTF { #1 }
+      {
+        \msg_error:nnnnn { groupthm } { wrong ~ definition }
+          { grouped ~ theorem } { #1 } { already }
+      }
+      {
+        \__groupthm_declare_grouped_theorem_aux:nnnn
+          { #1 } { #2 } { #3 } { #4 }
+      }
+  }
+\cs_generate_variant:Nn \groupthm_new_grouped_theorem:nnnn { n V V V }
+\cs_new:Npn \groupthm_provide_grouped_theorem:nnnn #1 #2 #3 #4
+  {
+    \cs_if_exist:cF { #1 }
+      {
+        \__groupthm_declare_grouped_theorem_aux:nnnn
+          { #1 } { #2 } { #3 } { #4 }
+      }
+  }
+\cs_generate_variant:Nn \groupthm_provide_grouped_theorem:nnnn { n V V V }
+\cs_new:Npn \groupthm_new_grouped_theorem_star:nnnn #1 #2 #3 #4
+  {
+    \groupthm_new_grouped_theorem:nnnn
+      { #1 } { #2, unnumbered } { #3 } { #4 }
+  }
+\cs_new:Npn \groupthm_provide_grouped_theorem_star:nnnn #1 #2 #3 #4
+  {
+    \groupthm_provide_grouped_theorem:nnnn
+      { #1 } { #2, unnumbered } { #3 } { #4 }
+  }
+\cs_new:Npn \groupthm_new_theorem:nnnn #1 #2 #3 #4
+  {
+    \groupthm_new_grouped_theorem:nnnn
+      { #1 } { #2 } { #3 } { #4 }
+    \groupthm_new_grouped_theorem:nnnn
+      { #1* } { #2, starred } { #3 } { #4 }
+  }
+\cs_generate_variant:Nn \groupthm_new_theorem:nnnn { n V V V }
+\cs_new:Npn \groupthm_provide_theorem:nnnn #1 #2 #3 #4
+  {
+    \groupthm_provide_grouped_theorem:nnnn
+      { #1 } { #2 } { #3 } { #4 }
+    \groupthm_provide_grouped_theorem:nnnn
+      { #1* } { #2, starred } { #3 } { #4 }
+  }
+\cs_generate_variant:Nn \groupthm_provide_theorem:nnnn { n V V V }
+\cs_new:Npn \groupthm_new_theorem_star:nnnn #1 #2 #3 #4
+  {
+    \groupthm_new_theorem:nnnn
+      { #1 } { #2, unnumbered } { #3 } { #4 }
+  }
+\cs_new:Npn \groupthm_provide_theorem_star:nnnn #1 #2 #3 #4
+  {
+    \groupthm_provide_theorem:nnnn
+      { #1 } { #2, unnumbered } { #3 } { #4 }
+  }
+\cs_new:Npn \groupthm_new_grouped_theorem_from_keys:nn #1 #2
+  {
+    \__groupthm_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_new_grouped_theorem:nVVV
+      { #1 }
+      \l__groupthm_key_group_clist
+      \l__groupthm_name_tl
+      \l__groupthm_key_thmtools_clist
+  }
+\cs_new:Npn \groupthm_provide_grouped_theorem_from_keys:nn #1 #2
+  {
+    \__groupthm_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_provide_grouped_theorem:nVVV
+      { #1 }
+      \l__groupthm_key_group_clist
+      \l__groupthm_name_tl
+      \l__groupthm_key_thmtools_clist
+  }
+\cs_new:Npn \groupthm_new_grouped_theorem_star_from_keys:nn #1 #2
+  {
+    \__groupthm_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_new_grouped_theorem_star:nVVV
+      { #2 }
+      \l__groupthm_key_group_clist
+      \l__groupthm_name_tl
+      \l__groupthm_key_thmtools_clist
+  }
+\cs_new:Npn \groupthm_provide_grouped_theorem_star_from_keys:nn #1 #2
+  {
+    \__groupthm_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_provide_grouped_theorem_star:nVVV
+      { #2 }
+      \l__groupthm_key_group_clist
+      \l__groupthm_name_tl
+      \l__groupthm_key_thmtools_clist
+  }
+\cs_new:Npn \groupthm_new_theorem_from_keys:nn #1 #2
+  {
+    \__groupthm_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_new_theorem:nVVV
+      { #2 }
+      \l__groupthm_key_group_clist
+      \l__groupthm_name_tl
+      \l__groupthm_key_thmtools_clist
+  }
+\cs_new:Npn \groupthm_provide_theorem_from_keys:nn #1 #2
+  {
+    \__groupthm_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_provide_theorem:nVVV
+      { #2 }
+      \l__groupthm_key_group_clist
+      \l__groupthm_name_tl
+      \l__groupthm_key_thmtools_clist
+  }
+\cs_new:Npn \groupthm_new_theorem_star_from_keys:nn #1 #2
+  {
+    \__groupthm_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_new_theorem_star:nVVV
+      { #1 }
+      \l__groupthm_key_group_clist
+      \l__groupthm_name_tl
+      \l__groupthm_key_thmtools_clist
+  }
+\cs_new:Npn \groupthm_provide_theorem_star_from_keys:nn #1 #2
+  {
+    \__groupthm_set_normalized_keys:nnn { #1 } { groupedtheorem } { #2 }
+
+    \groupthm_provide_theorem_star:nVVV
+      { #1 }
+      \l__groupthm_key_group_clist
+      \l__groupthm_name_tl
+      \l__groupthm_key_thmtools_clist
+  }
+\NewDocumentCommand{\NewGroupedTheorem}{s O{} m}
+  {
+    \IfBooleanTF{#1}
+    {
+      \groupthm_new_grouped_theorem_star_from_keys:nn { #2 } { #3 }
+    }
+    {
+      \groupthm_new_grouped_theorem_from_keys:nn { #2 } { #3 }
+    }
+  }
+\ProvideDocumentCommand{\NewGroupedTheorem}{s O{} m}
+  {
+    \IfBooleanTF{#1}
+    {
+      \groupthm_provide_grouped_theorem_star_from_keys:nn { #2 } { #3 }
+    }
+    {
+      \groupthm_provide_grouped_theorem_from_keys:nn { #2 } { #3 }
+    }
+  }
+\NewDocumentCommand{\NewTheorem}{s O{} m}
+  {
+    \IfBooleanTF{#1}
+    {
+      \groupthm_new_theorem_star_from_keys:nn { #2 } { #3 }
+    }
+    {
+      \groupthm_new_theorem_from_keys:nn { #2 } { #3 }
+    }
+  }
+\ProvideDocumentCommand{\NewTheorem}{s O{} m}
+  {
+    \IfBooleanTF{#1}
+    {
+      \groupthm_provide_theorem_star_from_keys:nn { #2 } { #3 }
+    }
+    {
+      \groupthm_provide_theorem_from_keys:nn { #2 } { #3 }
+    }
+  }
+\endinput
+%%
+%% End of file `groupthm.sty'.