A product for twelve Hadamard matrices

In 1867, Syvlester noted that the Kronecker product of two Hadamard matrices is an Hadamard matrix. This gave a way to obtain an Hadamard matrix of exponent four from two of exponent two. Early last decade, Agayan and Sarukhanyan found a way to combine two Hadamard matrices of exponent two to obtain one of exponent three, and just last year Craigen, Seberry and Zhang discovered how to combine four Hadamard matrices of exponent two to obtain one of exponent four. Using these products one can combine twelve Hadamard matrices of exponent two to obtain one of exponent ten. This paper describes how to obtain one of exponent nine.