HUIZINGH, Eelko. Applied statistics with SPSS. 1st ed. London : SAGE, 2007. viii, 356 s. Available on Internet: <http://www.loc.gov/catdir/toc/fy0711/2006928332.html> <http://www.loc.gov/catdir/enhancements/fy0728/2006928332-d.html> ISBN 978-1-4129-1931-9.