 A number of methods for constructing regular Hadamard matrices are known, and some exhaustive computer searches have been done for regular Hadamard matrices with specified symmetry groups, but it is not known whether every even perfect square is the order of a regular Hadamard matrix.Bush-type Hadamard matrices are regular Hadamard matrices of a special form, and are connected with finite projective planes.Like Hadamard matrices more generally, regular Hadamard matrices are named after Jacques Hadamard.