To cite fastSOM in publications use

  Stefan Kloessner Sven Wagner (2019). fastSOM: Calculation of
  Spillover Measures. R package version 1.0.1. URL
  http://CRAN.R-project.org/package=fastSOM

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {{fastSOM}: Calculation of Spillover Measures},
    author = {Stefan Kl\"o{\ss}ner and Sven Wagner},
    year = {2019},
    note = {R package version 1.0.1},
    url = {https://cran.r-project.org/package=fastSOM},
  }