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4. PKIX Working Group, Internet Engineering Task Force. “Internet Public Key Infrastructure: X.509 Certificate and CRL, Profile,” R. Housley, W. Ford, W. Polk, D. Solo, eds., work in progress. (Draft as of March, 1998, available from http://www.ietf.org/internet-drafts/draft-ietf-pkix-ipki-partl-07.txt.)