diff --git a/src/lib/CoAlgMisc.ml b/src/lib/CoAlgMisc.ml
index 4ed6e8843a8e086ddaac23375205f09fbec55e4a..4866e4fcea463b57a69a374a051d898e32d6344f 100644
--- a/src/lib/CoAlgMisc.ml
+++ b/src/lib/CoAlgMisc.ml
@@ -776,7 +776,11 @@ let atFormulaGetNominal f =
 
 let lfToAt _ lf = lf
 
+(* Calculate all possible formulae. This includes all subformulae and
+   in the case of μ-Calculus the Fischer-Ladner closure.
 
+   TODO: variable sort needs to match epected sort
+ *)
 let rec detClosure nomTbl hcF fset atset nomset s f =
   if s < 0 || s >= Array.length fset then
     let sstr = string_of_int s in