A. Bhagat, B. Sayankar, and P. Agrawal. International Journal on Recent and Innovation Trends in Computing and Communication, 3 (2):
545--548(February 2015)
A. Quinn, and B. Bederson. Proceedings of the 2011 annual conference on Human factors in computing systems, page 1403--1412. New York, NY, USA, ACM, (2011)
R. Poli, W. Langdon, and N. McPhee. Published via http://lulu.com and freely
available at
http://www.gp-field-guide.org.uk, (2008)(With contributions by J. R. Koza).