I'm looking to match a dataset I have assembled with patents and patent citations six years out from their date of application following Phene and Almeida (2008). Given that these variables are very common in strategic management literature, I'm surprised that this is so complicated. I have the firm name, GVKEY, and CUSIP identifiers. What is the best source for the date of a patent's application, the firm it was assigned to, and its citation count excluding self-citations? Thanks in advance for any help you can provide.