To cite the cobs package in publications use:

Pin T. Ng and Martin Maechler (2017). COBS -- Constrained B-splines (Sparse matrix based). R package version 1.3-3. URL https://CRAN.R-project.org/package=cobs

Ng P and Maechler M (2007). “A Fast and Efficient Implementation of Qualitatively Constrained Quantile Smoothing Splines.” Statistical Modelling, 7(4), pp. 315–328. http://smj.sagepub.com/content/7/4/315.abstract.

Corresponding BibTeX entries:

  @Manual{,
    title = {COBS -- Constrained B-splines (Sparse matrix based)},
    author = {Pin T. Ng and Martin Maechler},
    year = {2017},
    note = {R package version 1.3-3.},
    url = {https://CRAN.R-project.org/package=cobs},
  }

  @Article{,
    title = {A Fast and Efficient Implementation of Qualitatively
      Constrained Quantile Smoothing Splines},
    author = {Pin Ng and Martin Maechler},
    year = {2007},
    journal = {Statistical Modelling},
    volume = {7},
    number = {4},
    pages = {315--328},
    url = {http://smj.sagepub.com/content/7/4/315.abstract},
  }