This online textbook, Elementary Linear Algebra, is made available by Keith Matthews of the Department of Mathematics at the University of Queensland. Sections are organized into chapters such as Linear Equations, Matrices, Subspaces, Determinants, Complex Numbers, Eigenvalues and Eigenvectors, Identifying Second Degree Equations, and Three-dimensional Geometry. Each chapter features problems with the solutions available on-site. This is an excellent companion guide for college students taking linear algebra. In addition, the site includes an exact arithmetic matrix program, CMAT, that "performs exact calculations on matrices whose elements are rational numbers, complex rational numbers or numbers from a finite field of p (prime) elements." This program makes it easier to calculate problems such as the reduced row echelon form, the determinant, and the characteristic polynomial of a matrix.