To cite PTAk in publications use preferably the JSS one and the current version:

Package: PTAk
Version: 1.2-2
Date: 2010-16-5
Title: Principal Tensor Analysis on k modes
Author: Didier Leibovici     <didier.leibovici@nottingham.ac.uk>
Maintainer: Didier Leibovici <c3s2i@free.fr>
Depends:  tensor, tensorA
Description: A multiway method to decompose a tensor (array) of any order, as a generalisation of SVD also supporting non-identity metrics and penalisations. 2-way SVD with these extensions is also available. The package includes also some other multiway methods: PCAn (Tucker-n) and PARAFAC/CANDECOMP with these extensions.
License: GPL(>=2)
URL: http://c3s2i.free.fr/
 

  Leibovici, D. and Sabatier, R.(1998)A Singular Value Decomposition of k-Way Array for a Principal Component Analysis of Multiway Data,
  PTA-k. Linear Algebra and its Applications, 269:307-329

A BibTeX entry for LaTeX users is

  @Article{,
    title = {\textup{A Singular Value Decomposition of  \textit{k}-Way Array for
       a Principal Component Analysis of Multiway Data, \textsc{PTA}-\textit{k}}},
    author = {D. Leibovici and R. Sabatier},
    journal = {Linear Algebra and Its Applications},
    year = {1998},
    volume = {269},
    pages = {307-329},
  }
  Leibovici D.G. (2009) PTAk: Principal Tensor Analysis on k modes, R package version 1.2-0 .
  http://cran.r-project.org/web/packages/PTAk/index.html.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {\textup{PTAk}: \textup{Principal Tensor Analysis on k modes}},
    author = {Leibovici D.G.},
    year = {2009},
    edition = {R package version 1.1-20},
    url = {http://cran.r-project.org/web/packages/PTAk/index.html},
  }
  
  Leibovici D.G. (accepted in 2009) Spatio-Temporal Multiway Decompositions using Principal Tensor Analysis on k-modes: the R-package
  PTAk. Journal of Statistical Software. xx(x): 1-34.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {\textup{Spatio-Temporal Multiway Decompositions using Principal Tensor Analysis on k-modes: the  \textsc{R}-package \textsc{PTAk}}},
    author = {Leibovici D.G.},
    journal = {Journal of Statistical Software},
    year = {accepted in 2009},
    volume = {xx},
    pages = {1-34},
    number = {x},
  }
visit also http://c3s2i.free.fr or http://cgs.nottingham.ac.uk/~lgzdl
