To cite the original method in the 'nbc4va' package use (BioMed Central reference style):

Miasnikof P, Giannakeas V, Gomes M, Aleksandrowicz L, Shestopaloff AY, Alam D, Tollman S, Samarikhalaj, Jha P. Naive Bayes classifiers for verbal autopsies: comparison to physician-based classification for 21,000 child and adult deaths. BMC Medicine. 2015;13:286.<doi:10.1186/s12916-015-0521-2>.

Corresponding BibTeX entry:

  @Article{,
    title = {Naive Bayes classifiers for verbal autopsies: comparison
      to physician-based classification for 21,000 child and adult
      deaths},
    author = {Pierre Miasnikof and Vasily Giannakeas and Mireille Gomes
      and Lukasz Aleksandrowicz and Alexander Y. Shestopaloff and Dewan
      Alam and Stephen Tollman and Akram Samarikhalaj and Prabhat Jha},
    journal = {BMC Medicine},
    year = {2015},
    volume = {13},
    number = {286},
    url =
      {https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-015-0521-2},
  }