On Internet Authentication. - Neil Haller; Randall J. Atkinson (RFC, 1994)

The S/KEY One-Time Password System. - Neil Haller (RFC, 1995)

A One-Time Password System. - Neil Haller; Craig Metz (RFC, 1996)

A One-Time Password System. - Neil Haller; Craig Metz; Philip J. Nesser II; Mike Straw (RFC, 1998)