To cite validann in publications use:

Humphrey, G.B., Maier, H.R., Wu, W., Mount, N.J., Dandy, G.C., Abrahart, R.J., Dawson, C.W. (2017). Improved validation framework and R-package for artificial neural network models. Environmental Modelling & Software, 92, 82-106. URL http://doi.org/10.1016/j.envsoft.2017.01.023.

Corresponding BibTeX entry:

  @Article{,
    title = {Improved validation framework and R-package for artificial
      neural network models},
    author = {Greer B. Humphrey and Holger R. Maier and Wenyan Wu and
      Nick J. Mount and Graeme C. Dandy and Robert J. Abrahart and
      Christian W. Dawson},
    journal = {Environmental Modelling & Software},
    year = {2017},
    volume = {92},
    pages = {82--106},
    url = {http://doi.org/10.1016/j.envsoft.2017.01.023},
  }