--- a/farolluz/document.py	Mon Dec 29 15:00:59 2014 +0100
+++ b/farolluz/document.py	Mon Dec 29 16:33:34 2014 +0100
@@ -82,6 +82,7 @@
 class CVRFTracking(object):
     STATUSES = ('Draft', 'Interim', 'Final')
     def __init__(self, _id, status, version, initial, current):
+        """ version must be a tuple of (max four) ints """
         self._identification = _id
         self._status = status
         self._version = version
@@ -148,6 +149,7 @@
 
 class CVRFRevision(object):
     def __init__(self, number, date, description):
+        """ number is a tuple of (max four) ints """
         self._number = number
         self._date = date
         self._description = description