A theorem in least squares
C. Radhakrishna Rao · 1951
(0.1) A row vector a = (ax, a2,...,am) is always represented by a Greek letter and its elements by lower case italics. A matrix (a{?) consisting of n rows and m columns is denoted by a capital letter. Thus A = (a^). (0.2) The row vectors in A are represented by ax,..., an and the column vectors by /?!,...,?m. The rank of the matrix A is equal to the number of independent vectors in the a set which is same as that in the ? set. (0.3) Any vector of m elements can be represented by a linear combination of a set of m independent vectors each of m elements.