To cite stm in publications use:

Roberts ME, Stewart BM, Tingley D (2019). “stm: An R Package for Structural Topic Models.” Journal of Statistical Software, 91(2), 1–40. doi: 10.18637/jss.v091.i02.

Corresponding BibTeX entry:

  @Article{,
    title = {{stm}: An {R} Package for Structural Topic Models},
    author = {Margaret E. Roberts and Brandon M. Stewart and Dustin
      Tingley},
    journal = {Journal of Statistical Software},
    year = {2019},
    volume = {91},
    number = {2},
    pages = {1--40},
    doi = {10.18637/jss.v091.i02},
  }