A.M. Carvalho
http://www.sciencedirect.com/science/article/pii/S0926669014007985
http://www.sciencedirect.com/science/article/pii/S0926669013005529
http://www.sciencedirect.com/science/article/pii/S0278691507001949
http://www.sciencedirect.com/science/article/pii/S0278691508000756
http://www.sciencedirect.com/science/article/pii/S0278691508001439