Most of the patent reference data on this site was build from bulk downloads the uspto
made available. datamp.org
graciously provided additional data as shown below.
(being a developer of datamp.org has its benefits!)
Students of mathematics may notice an apparent discrepancy. The counts shown are unique patents.
The data from datamp.org contained multiple patentees when applicable so there can be multiple references to the same patent. Ex. Patent 1,041,451 was issued to George O. Leopold and Thomas J. Fegley.
It was added to the reference table here twice. Once as "Leopold et al." and once
as "Fegley et al.". A user's search here could find either. The uspto data generally
only ed al.'s the first patentee listed (they'd only have "Fegley et al." as Thomas is listed first on the example patent).
¹ The Patentsview.org data is covered by the Creative Commons
Attribution 4.0 License. Apparently all I have to
do is credit the source, provide a link to the license and state if I've made changes. Oh, and I'm not to suggest that the licensor endorses me or my use of their data. For the record
I used their uspatentcitation.tsv and I made no changes to the 35,888 rows of pre-1920 references that I did not already have.