1.1 --- a/TODO.md	Tue Aug 10 12:56:06 2021 +0200
     1.2 +++ b/TODO.md	Tue Aug 10 12:58:33 2021 +0200
     1.3 @@ -28,7 +28,10 @@
     1.4      shall be done in connection with cf. e587c45cae0f note in Build_Thydata.thy
     1.5  
     1.6  * What is the idea behind KEStore_Elems.add_thes? How to do it properly in current Isabelle?
     1.7 -    cf. e587c45cae0f note in Build_Thydata.thy
     1.8 +    https://static.miraheze.org/isacwiki/0/04/Isac-docu.pdf distinguishes 
     1.9 +    several kinds of ISAC users, in particular "math author (Mathematik-Autor)" and
    1.10 +    "course designer (Kurs-Designer)". The latter just adds examples which re-use existing
    1.11 +    knowledge designed by the former. KEStore_Elems.add_thes is an interface for the latter.   
    1.12  
    1.13  * WN: clarify add_calcs with non-existant constant "Integrate.add_new_c";
    1.14