Boron-nitrogen chemistry / Kurt Niedenzu, symposium chairman. (OCLC #665449)
This series this monograph is in is usually classed together, so the call number in the OCLC record uses the class number in the series authority record:
050 _0 ǂa QD1 ǂb .A355
with the enumeration appended:
050 00 ǂa QD1 ǂb .A355 no. 42
The enumeration “no. 42” was also included on the item record, so the volume label (printed prior to the year 2000) included it twice:
QD1 .A355 no. 42 no. 42
I’ve corrected the catalog and sent the volume to labeling, probably to have part of it covered with a small white sticker.