By putting a set of MOLS() in standard form and examining the entries in the second row and first column of each square, it can be seen that no more than squares can exist. A set of − 1 MOLS() is called a "complete set of MOLS". Complete sets are known to exist when is a prime number or power of a prime (see Finite field construction below). However, the number of MOLS that may exist for a given order is not known for general , and is an area of research in combinatorics.