To cite package ‘rWikiPathways’ in publications use:

  Slenter, N. D, Kutmon, M., Hanspers, K., Riutta, A., Windsor, J.,
  Nunes, N., Melius, J., Cirillo, E., Coort, L. S, Digles, D., Ehrhart,
  F., Giesbertz, P., Kalafati, M., Martens, M., Miller, R., Nishida,
  K., Rieswijk, L., Waagmeester, A., Eijssen, T. LM, Evelo, T. C, Pico,
  R. A, Willighagen, L. E (2018). “WikiPathways: a multifaceted pathway
  database bridging metabolomics to other omics research.” _Nucleic
  Acids Res._, *46*(D1), D661-D667.

A BibTeX entry for LaTeX users is

  @Article{,
    author = {{Slenter} and D. N. and {Kutmon} and {M.} and {Hanspers} and {K.} and {Riutta} and {A.} and {Windsor} and {J.} and {Nunes} and {N.} and {Melius} and {J.} and {Cirillo} and {E.} and {Coort} and S. L. and {Digles} and {D.} and {Ehrhart} and {F.} and {Giesbertz} and {P.} and {Kalafati} and {M.} and {Martens} and {M.} and {Miller} and {R.} and {Nishida} and {K.} and {Rieswijk} and {L.} and {Waagmeester} and {A.} and {Eijssen} and L. M. T. and {Evelo} and C. T. and {Pico} and A. R. and {Willighagen} and E. L.},
    title = {{{W}iki{P}athways: a multifaceted pathway database bridging metabolomics to other omics research}},
    journal = {Nucleic Acids Res.},
    year = {2018},
    volume = {46},
    number = {D1},
    pages = {D661-D667},
    month = {Jan},
  }