On Orthogonality of Latin Squares
  An arrangement of s elements in s rows and s columns, such that no element repeats more than once in each row and each column is called a Latin square of order s. If two Latin squares of the same order superimposed one on the other and in the resultant array if each ordered pair occurs once and only once then they are called othogonal Latin Squares. A frequency square is an nxn matrix, such that each element from the list of n elements, occurs t times in each row and in each column. These two concepts lead to a new third concept called as t orthogonal latin squares, where from a set of m orthogonal Latin squares, if t orthogonal Latin squares are superimposed and each ordered t tuple in the resultant array occurs once and only once then it is t othogonal Latin square. In this paper it is proposed to construct such t othogonal latin squares 
R.N.Mohan, Moon Ho Lee, and Subash Pokreal