Nulls in cited patents

The uspto (and hence patentsview) has full data for patents issued in 1976 and above. Only a handful of fields are available for pre 1976 patents at (issue date, uspcs, cpcs and obviously patent number). The reference table below is copied from for patent D756514 If you compare the reference table to the patentsview data for that patent you'll see that the nulls returned by patentsview correspond to the pre 1976 patents referenced. It makes sense that the titles wouldn't come back but at a minimum I think the patent number should be returned.

Patents Cited in D756514
563421July 1896Sheppard
3247324April 1966Cefaly et al.
3618697November 1971Littmann et al.
D379935June 1997Jornacion
6883639April 2005Lam et al.
D536448February 2007Jackson

Data returned by patentsview