Add fields of documents in FindRD collections

README.rst

@@ -98,4 +98,16 @@ something about it, e.g.:
 - sends an email to the FDM team
 
 
+Documents
+---------
+
+The documents in the collections “findings” and “items” must have a “``pid``”
+field.  This is the prime PID.  The rest is optional:
+
+- ``institute``
+- ``pof4_topic``
+- ``aliases`` (alias PIDs)
+- ``email`` (of contact person)
+- …
+
 ..  LocalWords:  FindRD