Elementary Linear Algebra: Applications Version, 11th Edition (http://bcs.wiley.com/he-bcs/Books?action=index&itemId=1118434412&bcsId=8466)

Introduction to linear independence (https://www.khanacademy.org/math/linear-algebra/vectors-and-spaces/linear-independence/v/linear-algebra-introduction-to-linear-independence)

Linear combinations and span(https://www.khanacademy.org/math/linear-algebra/vectors-and-spaces/linear-combinations/v/linear-combinations-and-span)