diff --git a/scripts/lectures.py b/scripts/lectures.py
index 71a737d..b027cc4 100755
--- a/scripts/lectures.py
+++ b/scripts/lectures.py
@@ -83,7 +83,7 @@ class Lectures(list):
         elif string == 'prev':
             return self[-1].number - 1
 
-    def parse_range_string(self, arg):
+    def parse_range_string_section(self, arg):
         all_numbers = [lecture.number for lecture in self]
         if 'all' in arg:
             return all_numbers
@@ -94,6 +94,10 @@ class Lectures(list):
 
         return [self.parse_lecture_spec(arg)]
 
+    def parse_range_string(self, arg):
+        sets = [set(self.parse_range_string_section(part)) for part in arg.split(',')]
+        return list(set.union(*sets))
+
     def new_lecture(self):
         if len(self) != 0:
             new_lecture_number = self[-1].number + 1