ht t p://www.cse.iit b.ac.in/~ CS709/not es/LinearAlgebra.pdf
ht t p://en.wikipedia.org/wiki/Cauchy% E2% 80% 93Schwarz _inequalit y
ht t p://www.cse.iit b.ac.in/~ cs709/calendar2013.ht m l
ht t p://www.m at h.ucsd.edu/~ njw/Teaching/Mat h271C/Lect ure_04.pdf