@article{girstmair:1990:dcc,
    author = {Girstmair, Kurt},
     title = {{D}irichlet convolution of cotangent numbers and relative class
              number formulas},
   journal = {Monatsh. Math.},
  fjournal = {Monatshefte f\"ur Mathematik},
    volume = {110},
      year = {1990},
    number = {3-4},
     pages = {231–256},
      issn = {0026-9255},
     coden = {MNMTA2},
   mrclass = {11R18 (11R20 11R29)},
  mrnumber = {MR1084314 (92b:11076)},
mrreviewer = {Peter Stevenhagen},
     zblno = {0717.11048}}