To cite libstable4u in publications use:

  Royuela-del-Val J, Simmross-Wattenberg F, Alberola-López C (2017).
  “libstable: Fast, Parallel, and High-Precision Computation of
  $\alpha$-Stable Distributions in R, C/C++, and MATLAB.” _Journal of
  Statistical Software_, *78*(1), 1-25. doi:10.18637/jss.v078.i01
  <https://doi.org/10.18637/jss.v078.i01>.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {{libstable}: Fast, Parallel, and High-Precision Computation of $\alpha$-Stable Distributions in {R}, {C/C++}, and {MATLAB}},
    author = {Javier Royuela-del-Val and Federico Simmross-Wattenberg and Carlos Alberola-L{\'o}pez},
    journal = {Journal of Statistical Software},
    year = {2017},
    volume = {78},
    number = {1},
    pages = {1--25},
    doi = {10.18637/jss.v078.i01},
  }