To cite SNPRelate in publications use:

  Xiuwen Zheng, David Levine, Jess Shen, Stephanie M. Gogarten, Cathy
  Laurie, Bruce S. Weir. A High-performance Computing Toolset for
  Relatedness and Principal Component Analysis of SNP Data.
  Bioinformatics 2012; doi: 10.1093/bioinformatics/bts606

A BibTeX entry for LaTeX users is

  @Article{,
    title = {A High-performance Computing Toolset for Relatedness and Principal Component Analysis of SNP Data},
    author = {Xiuwen Zheng and David Levine and Jess Shen and Stephanie Gogarten and Cathy Laurie and Bruce Weir},
    journal = {Bioinformatics},
    year = {2012},
    doi = {10.1093/bioinformatics/bts606},
    volume = {28},
    number = {24},
    pages = {3326-3328},
  }