M. Kaltenbäck, H. Winkler, H. Woracek:
"Almost Pontryagin Spaces";
Operator Theory: Advances and Applications, 160 (2005), 253 - 271.
http://aleph.ub.tuwien.ac.at/F?base=tuw01&func=find-c&ccl_term=AC05937687
Project Head Heinz Langer:
RTN Analysis and Operators