R. Brumana, D. Oreni, A. Raimondi, A. Georgopoulos, and A. Bregianni. The Institute of Electrical and Electronics Engineers, Inc. (IEEE) Conference Proceedings, 1, page 497. Piscataway, The Institute of Electrical and Electronics Engineers, Inc. (IEEE), (October 2013)
R. Aviv, Z. Erlich, and G. Ravid. The 3rd IEEE International Conference on Advanced Learning Technologies, 2003. Proceedings, page 145 -- 149. (July 2003)