To cite wnominate in publications use:

Poole K, Lewis J, Lo J, Carroll R (2011). “Scaling Roll Call Votes with wnominate in R.” Journal of Statistical Software, 42(14), 1–21. https://www.jstatsoft.org/v42/i14/.

Corresponding BibTeX entry:

  @Article{,
    entry = {Article},
    title = {Scaling Roll Call Votes with {wnominate} in {R}},
    author = {Keith Poole and Jeffrey Lewis and James Lo and Royce
      Carroll},
    journal = {Journal of Statistical Software},
    year = {2011},
    volume = {42},
    number = {14},
    pages = {1--21},
    url = {https://www.jstatsoft.org/v42/i14/},
  }