SMTP on X.25. - Robert Ullmann (RFC, 1989)

Encoding header field for internet messages. - David Robinson; Robert Ullmann (RFC, 1990)

New DNS RR Definitions. - Craig Everhart; Louis A. Mamakos; Robert Ullmann; Paul V. Mockapetris (RFC, 1990)

Multiprotocol Interconnect on X.25 and ISDN in the Packet Mode. - Andrew G. Malis; David Robinson; Robert L. Ullmann (RFC, 1992)

TP/IX: The Next Internet. - Robert Ullmann (RFC, 1993)

RAP: Internet Route Access Protocol. - Robert Ullmann (RFC, 1993)

Encoding Header Field for Internet Messages. - Albert K. Costanzo; David Robinson; Robert Ullmann (RFC, 1993)

CATNIP: Common Architecture for the Internet. - Michael McGovern; Robert Ullmann (RFC, 1994)