Rudin 1976, ப. 206. A mapping A of a vector space X into a vector space Y is said to be a linear transformation if: for all and all scalars c. Note that one often writes instead of if A is linear. Rudin, Walter (1976). Principles of Mathematical Analysis. Walter Rudin Student Series in Advanced Mathematics (3rd ed.). New York: McGraw–Hill. ISBN978-0-07-054235-8.