An Analog VLSI Chip for Finding Edges from Zero-crossings.

Wyeth Bair Christof Koch An Analog VLSI Chip for Finding Edges from Zero-crossings. 399-405 http://nips.djvuzone.org/djvu/nips03/0399.djvu 1990 conf/nips/1990 NIPS db/conf/nips/nips1990.html#BairK90