Links
[1] http://www.loc.gov/aba/pcc/bibco/nonfile.html
[2] http://web.library.yale.edu/cataloging/end-punct-var-fields
[3] http://lcweb.loc.gov/marc/bibliographic/bdapp-e.html
[4] http://lcweb.loc.gov/marc/
[5] http://www.loc.gov/marc/umb/
[6] http://www.loc.gov/marc/mac/index.html
[7] http://www.loc.gov/standards/valuelist/