To cite R/qtlbook in publications use:

Broman K, Sen Ś (2009). A Guide to QTL Mapping with R/qtl. Springer, New York. doi:10.1007/978-0-387-92125-9, https://doi.org/10.1007/978-0-387-92125-9.

Corresponding BibTeX entry:

  @Book{,
    title = {A Guide to {QTL} Mapping with {R}/qtl},
    author = {Karl W. Broman and Śaunak Sen},
    publisher = {Springer},
    year = {2009},
    address = {New York},
    doi = {10.1007/978-0-387-92125-9},
    url = {https://doi.org/10.1007/978-0-387-92125-9},
  }