diff --git a/cpdfchop.ml b/cpdfchop.ml
index faf582c..cbd9703 100644
--- a/cpdfchop.ml
+++ b/cpdfchop.ml
@@ -1,5 +1,12 @@
 open Pdfutil
 open Cpdferror
 
+(* Prevent duplication of content by sharing content streams *)
+(* Resources - patterns etc. - pattern matrices *)
+(* Bookmarks: merge/duplicate them *)
+(* Annotations: merge/duplicate them *)
+(* Page boxes - mediabox or cropbox used? Output modifies all boxes? *)
+(* fast/slow *)
+
 (* Chop pages into pieces *)
 let chop ~x ~y pdf range = pdf