A National-Scale Authentication Infrastructur. - Randy Butler; Von Welch; Douglas Engert; Ian T. Foster; Steven Tuecke; John Volmer; Carl Kesselman (Computer, 2000)

Internet X.509 Public Key Infrastructure (PKI) Proxy Certificate Profile. - Steven Tuecke; Von Welch; Douglas Engert; Laura Pearlman; Mary R. Thompson (RFC, 2004)