Christopher Cahill has co-authored the definitive work on federal rules with respect to adding defendants to complaints after the expiration of the period set by law to file such a complaint.  The article is published in the  February 2014 edition of the Norton Journal of Bankruptcy Law & Practice.  The full citation is:  Christopher M. Cahill & Edward E. Neiger, Adding Defendants to Preference Complaints after Expiration of the Limitations Period: A Guide to Amendment and Relation Back after Krupski v. Costa Crociere, 23 J. Bankr. L. & Prac. NL 1 Art. 3 (Feb. 2014).