To cite UBL in publications use:

Paula Branco, Rita P. Ribeiro, Luis Torgo (2016)., UBL: an R Package for Utility-Based Learning, CoRR abs/1604.08079 [cs.MS], URL: http://arxiv.org/abs/1604.08079

Corresponding BibTeX entry:

  @Article{,
    title = {{UBL}: an R Package for Utility-Based Learning},
    author = {Paula Branco and Rita P. Ribeiro and Luis Torgo},
    year = {2016},
    ee = {http://arxiv.org/abs/1604.08079},
    volume = {abs/1604.08079},
    journal = {CoRR},
  }