Who cites whom most often
John Ioannidis from Stanford has analysed citations pattern. In this 2016 paper he looks at citation patterns in multi-authorship. He commented on the impact of alphabetic authoring in the various disciplines as well.  

In a recent August study in PLoS Biology, John further explores self-citations as well. In this paper he examines "extreme self-citations and citation farms" that can skew and game the citation system. 

So yes, using his technique (he examines the Scopus and GoogleScholar database in these studies), you can probably find and examine citation patterns as well.