Ow did Charlie Chaplin, Buster Keaton, and Harold Lloyd use the form of slapstick comedy in silent film?

I would like use the following books for 4 of the sources:
-The Silent Clowns by Walter Kerr
-The Parade s Gone By& by Kevin Brownlow
-Silent Comedy by Paul Merton
-Harlequins stick, Charlies cane: a comparative study of commedia dellarte and silent slapstick comedy by David Madden

I am not allowed to use internet sources.

I would also like to reference the following 3 films:
Safety Last by Harold Lloyd
Easy Street by Charlie Chaplin
Sherlock Jr. by Buster Keaton