Films or motion pictures are frequently based on literature and plays. More sources can be found in Summon with subject headings such as:
A Companion to film theory / edited by Toby Miller and Robert Stam.
Malden, Mass : Blackwell, 1999.
PN1995 .C667 1999
A companion to literature and film / edited by Robert Stam and Alessandra Raengo.
Malden, MA : Blackwell Pub., 2004
PN1995.3 .C65 2004
The Oxford handbook of film and media studies / edited by Robert Kolker.:New York : Oxford University Press, 2008.
Bird-Reference, 2nd Floor (does not circulate) PN1994 .O93 2008
International dictionary of films and filmmakers / editor, Nicholas Thomas ; consulting editor, James Vinson.Chicago : St. James Press, c1990-1994. Vol. 1-5 Bird-Reference, 2nd Floor (does not circulate) PN1997.8 .I58 1990
The databases where you can find articles are not in an alphabetical order and NOT according to importance, since each researcher will have a different thesis and needs.