R. Theja, G. Kalyani, and K. Jyothi. International Journal on Recent and Innovation Trends in Computing and Communication, 3 (4):
1746--1749(April 2015)
V. Tablan, I. Roberts, H. Cunningham, and K. Bontcheva. Philosophical Transactions of the Royal Society A: Mathematical, Physical & Engineering Sciences, 371 (1983):
20120071(2013)