Sui generis | Webster's Dictionary of the English Language

sui
sŭi (gen.), dat. sĭbī̆, acc. and abl. sē or sēsē, sing. and plur. (old dat. sĭbei, C. I. L. 1, 38;...

A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.
sui
suī (gen.), dat.sibi or sibī, acc.and abl.sē or (more emphatic) sēsē (strengthened sēpse for sē ips...

An Elementary Latin Dictionary