To cite the cobs package in publications use:

  Pin T. Ng and Martin Maechler (2024). COBS -- Constrained B-splines
  (Sparse matrix based). R package version 1.3-9. URL
  https://CRAN.R-project.org/package=cobs

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {COBS -- Constrained B-splines (Sparse matrix based)},
    author = {Pin T. Ng and Martin Maechler},
    year = {2024},
    note = {R package version 1.3-9.},
    url = {https://CRAN.R-project.org/package=cobs},
  }

  Ng P, Maechler M (2007). “A Fast and Efficient Implementation of
  Qualitatively Constrained Quantile Smoothing Splines.” _Statistical
  Modelling_, *7*(4), 315-328. doi:10.1177/1471082X0700700403
  <https://doi.org/10.1177/1471082X0700700403>.

A BibTeX entry for LaTeX users is

  @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},
    doi = {10.1177/1471082X0700700403},
  }