diff --git a/m-bitset.h b/m-bitset.h
index 9b794403..25fdc10e 100644
--- a/m-bitset.h
+++ b/m-bitset.h
@@ -474,6 +474,6 @@ bitset_get_str(string_t str, const bitset_t set, bool append)
    ,EQUAL(bitset_equal_p)                                               \
    )
 
-// TODO: set_at2, insert_v, remove_v, shrink_to_fit,
+// TODO: set_at2, insert_v, remove_v, shrink_to_fit, hash
 
 #endif
diff --git a/m-rbtree.h b/m-rbtree.h
index b9d238f3..1e12d31c 100644
--- a/m-rbtree.h
+++ b/m-rbtree.h
@@ -747,6 +747,8 @@ typedef enum {
 
 // TODO: missing specialized iterator functions (it_from, it_to)
 // TODO: _get_str, _in_str, _out_str: how to print them?
+// TODO: equal. Can be difficult since 2 trees can be functionaly equal, but structuraly different
+// (no unique representation). Same problem for hash.
 // TODO: specialized _sort shall do nothing, but shall check the requested order. How ?