To cite package 'mixture' in publications use:

Ryan P. Browne and Paul D. McNicholas (2013). mixture: Mixture Models for Clustering and Classification. R package version 1.0.
Ryan P. Browne and Paul D. McNicholas (2013). Estimating Common Principal Components in High Dimensions. Arxiv preprint arXiv:1302.2102.
Ryan P. Browne and Paul D. McNicholas (2012). Orthogonal Stiefel Manifold Optimization for Eigen-Decomposed Covariance Parameter Estimation in Mixture Models. Statistics and Computing. To appear.
Gilles Celeux and Gerard Govaert (1995). Gaussian Parsimonious Clustering Models. Pattern Recognition. 28(5), 781-793.

Corresponding BibTeX entries:

  @Manual{,
    title = {mixture: Mixture Models for Clustering and
      Classification},
    author = {Ryan P. Browne and Paul D. McNicholas},
    year = {2013},
    note = {R package version 1.0},
  }
  @TechReport{,
    title = {Estimating Common Principal Components in High
      Dimensions},
    author = {Ryan P. Browne and Paul D. McNicholas},
    year = {2013},
    institution = {Arxiv preprint},
    number = {arXiv:1302.2102},
  }
  @Article{,
    title = {Orthogonal Stiefel Manifold Optimization for
      Eigen-Decomposed Covariance Parameter Estimation in Mixture
      Models},
    author = {Ryan P. Browne and Paul D. McNicholas},
    year = {2012},
    journal = {Statistics and Computing},
  }
  @Article{,
    title = {Gaussian Parsimonious Clustering Models},
    author = {Gilles Celeux and Gerard Govaert},
    year = {2012},
    journal = {Pattern Recognition},
    volume = {28},
    number = {5},
    pages = {781-793},
  }