http://www.eas.uccs.edu/wickert/ece2610/lecture_notes/ece2610_chap9.pdf 

http://courses.ece.ubc.ca/359/lectures/chapter2.pdf

http://www.site.uottawa.ca/~jpyao/courses/ELG3120_files/ch2.pdf

http://www.javaquant.net/papers/Laplacetransform.pdf

http://www.secs.oakland.edu/~frick/ECE276_W11_ICN/Laplace_Notes.pdf

http://books.google.com/books?id=MQPeFiB9cSQC&pg=PA363&lpg=PA363&dq=LTI+systems+analytic&source=bl&ots=59dK4ldJiH&sig=RKj4z7ZFpqkY6dqiJqv05fT9rDM&hl=en&sa=X&ei=Fv_mUKCbF7Ck0AWw5YCgDQ&ved=0CGAQ6AEwCTgK