Prepared for consideration by the Network Technical Architecture Group (NTAG), a subcommittee of the Library of Congress (LC) Network Advisory Group, this document describes the study and development of text formats for the message delivery system of a nationwide library bibliographic network. Following a discussion of network considerations of the National Commission on Library and Information Science (NCLIS)/National Bureau of Standards (NBS) end to end computer protocol, an explanation is given of 13 command codes, 4 status codes, and 7 response codes which could be used to communicate between the many different types of computers in the proposed nationwide network. The key structure of search arguments is then identified for index types used by eight online bibliographic utilities or libraries with online systems, including: LC, the National Library of Medicine (NLM), OCLC, the University of Chicago, the Washington Library Network (WLN), Northwestern University, the New York Public Library, and BALLOTS. In order to facilitate cross-system comparison, the key structure of search arguments is also presented by type of file index. Author/title, CODEN, corporate/conference name, International Standard Book Number (ISBN), International Standard Serial Number (ISSN), LC classification number, personal name, subject, and title indexes are included. Finally, network standard search argument syntaxes are suggested for each type of index. (ESR)