Oscar H. Ibarra Sara Woodworth Hsu-Chun Yen Zhe Dang On the Computational Power of 1-Deterministic and Sequential P Systems. 133-152 2006 73 Fundam. Inform. 1-2 http://iospress.metapress.com/openurl.asp?genre=article&issn=0169-2968&volume=73&issue=1&spage=133 db/journals/fuin/fuin73.html#IbarraWYD06