To cite somoclu in publications use:

  Peter Wittek, Shi Chao Gao, Ik Soo Lim, Li Zhao (2017). somoclu: An
  Efficient Parallel Library for Self-Organizing Maps. Journal of
  Statistical Software, 78(9), 1-21. doi:10.18637/jss.v078.i09

A BibTeX entry for LaTeX users is

  @Article{,
    title = {{somoclu}: An Efficient Parallel Library for Self-Organizing Maps},
    author = {Peter Wittek and Shi Chao Gao and Ik Soo Lim and Li Zhao},
    journal = {Journal of Statistical Software},
    year = {2017},
    volume = {78},
    number = {9},
    pages = {1--21},
    doi = {10.18637/jss.v078.i09},
  }