diff --git a/src/Language.ml b/src/Language.ml
index 9b6d9ac72..0fb34aba0 100644
--- a/src/Language.ml
+++ b/src/Language.ml
@@ -70,7 +70,12 @@ module Expr =
       | Var   x -> st x
       | Binop (op, x, y) -> to_func op (eval st x) (eval st y)
 
-    (* Expression parser *)
+    (* Expression parser. You can use the following terminals:
+
+         IDENT   --- a non-empty identifier a-zA-Z[a-zA-Z0-9_]* as a string
+         DECIMAL --- a decimal constant [0-9]+ as a string
+                                                                                                                  
+    *)
     ostap (                                      
       parse:
 	  !(Ostap.Util.expr 
@@ -93,7 +98,7 @@ module Expr =
       | x:IDENT   {Var x}
       | -"(" parse -")"
     )
-
+    
   end
                     
 (* Simple statements: syntax and sematics *)
diff --git a/src/SM.ml b/src/SM.ml
index e3e985860..6b6d9b865 100644
--- a/src/SM.ml
+++ b/src/SM.ml
@@ -16,7 +16,7 @@ type prg = insn list
 (* The type for the stack machine configuration: a stack and a configuration from statement
    interpreter
  *)
-type config = int list * Language.Stmt.config
+type config = int list * Stmt.config
 
 (* Stack machine interpreter