science direct

http://ac.els-cdn.com/B9780123970312000084/3-s2.0-B9780123970312000084-main.pdf?_tid=e167023c-7630-11e4-949f-00000aab0f01&acdnat=1417091484_7e5d52820192f24e2e03cda618587227

http://www.sciencedirect.com/science/article/pii/B9780124167148000019


http://ac.els-cdn.com/S0001691814002315/1-s2.0-S0001691814002315-main.pdf?_tid=e078ef9c-7631-11e4-b2f9-00000aacb362&acdnat=1417091912_d3779f3af0611c7474f8aa1b557e9a97