MARC/PERL: a Perl 5 library for reading, manipulating, outputting and converting bibliographic records in the MARC format: http://marcpm.sourceforge.net/
MARC e XML: http://www.loc.gov/standards/iso25577/
UNIMARC to MARC 21 Conversion Specifications Version 3.0 (August 2001): http://www.loc.gov/marc/unimarctomarc21.html
Jay Weitz: OCLC's UNIMARC/MARC 21 Conversion: http://www.ifla.org/IV/ifla67/papers/001-188e.pdf
Zeno Tajoli: Da Unimarc a MARC21 (Bollettino del Cilea n. 95 (dicembre 2004), pp. 27-28): http://eprints.rclis.org/archive/00002819/
MarcEdit (strumento per editare record MARC): http://oregonstate.edu/~reeset/marcedit/html/tech.html