showkeys – Show label, ref, cite and bib keys

The showkeys pack­age mod­i­fies the \la­bel, \ref, \pageref, \cite and \bib­item com­mands so that the ‘in­ter­nal’ key is printed, with­out af­fect­ing the ap­pear­ance of the rest of the text, so far as is pos­si­ble (the keys typ­i­cally ap­pear in the mar­gin).
The pack­age is part of the tools bun­dle in the LaTeX re­quired dis­tri­bu­tion.