See Karoubi and Adem
arXiv: Experimental full text search
NCG (Algebra and noncommutative geometry)
Two papers by Cuntz and Quillen: On Excision in Periodic Cyclic Cohomology. In Comptes Rendus, no electronic version as of Aug 09. Proves a six-term exact sequence for a short exact sequence associated to an ideal in an algebra over a field of char zero.
nLab page on Periodic cyclic cohomology