If you use qgam please cite our paper:

Fasiolo M., Goude Y., Nedellec R. and Wood S. N. (2018). Fast calibrated additive quantile regression. URL: https://arxiv.org/abs/1707.03307

Corresponding BibTeX entry:

  @Manual{,
    title = {Fast calibrated additive quantile regression.},
    author = {Matteo Fasiolo and Yannig Goude and Raphael Nedellec and
      Simon N. Wood},
    year = {2018},
    url = {https://arxiv.org/abs/1707.03307},
  }