See if your library can dig up a copy of Scientific American, April 1973. Martin Grdner's column is all about Negabinaries. Unfortunatly http://www.sciam.com/ only has back issues from 1998 online. But they do publish an archival CD maybe your library will have that.

I also found several articles/papers concerning Negabinaries in Optics and VLSI. Search at www.google.com for negabinary.

It would appear that coming up with a decimal to negabinary converter is a favourite assignment for Comp-sci profs. :)

Good Luck

mitd-Made in the Dark
'My favourite colour appears to be grey.'