Prepare fee lookups.

MODULES.md

@@ -219,6 +219,14 @@ Returns the total duration in months of the periods given in the list
 ```l```. Each period is represented as ```(list start-month
 end-month)```.
 
+	(month-in-periods p [m (*current-month*)])
+
+* ```p``` - a periods
+* ```m``` - a valid month - defaults to ```(*current-month*)```
+
+Returns ```#t``` if given month ```m``` lies within the period
+```p```.
+
 	(month-in-periods? ps [m (*current-month*)])
 
 * ```ps``` - a list of periods