Mass Transfer Driving Force....

For our purposed we need to look into two film resistance theory (...i think) also known as two-film theory. i am currently working through Fundamentals of Momentum Heat and Mass Transfer by Welty, Wicks, Wilson and Rorrer. it has a good chapter on one phase mass transfer and two phase mass transfer so from a liquid to say gas! the other book is literally written in a language i don't understand.