To cite truncSP in publications use:

Karlsson M, Lindmark A (2014). “truncSP: An R Package for Estimation of Semi-Parametric Truncated Linear Regression Models.” Statistics in Medicine, 57(14), 1–19. https://www.jstatsoft.org/article/view/v057i14.

Corresponding BibTeX entry:

  @Article{,
    title = {{truncSP}: An {R} Package for Estimation of
      Semi-Parametric Truncated Linear Regression Models},
    author = {Maria Karlsson and Anita Lindmark},
    journal = {Statistics in Medicine},
    year = {2014},
    volume = {57},
    number = {14},
    pages = {1--19},
    url = {https://www.jstatsoft.org/article/view/v057i14},
  }