Parallel meanings within tags:

Within the 1XX, 4XX, 6XX, 7XX and 8XX blocks, certain parallels of content designation are usually preserved. The following meanings, with some exceptions, are given to the final two characters of the tag of fields:

X00 Personal names

X10 Corporate names

X11 Meeting names

X30 Uniform titles

X40 Bibliographic titles

X50 Topical terms

X51 Geographic names