Richard Banach Czeslaw Jeske Michael Poppleton Susan Stepney Retrenching the Purse: The Balance Enquiry Quandary, and Generalised and (1, 1) Forward Refinements. 29-69 2007 77 Fundam. Inform. 1-2 http://iospress.metapress.com/openurl.asp?genre=article&issn=0169-2968&volume=77&issue=1&spage=29 db/journals/fuin/fuin77.html#BanachJPS07