In this paper it is shown that an Hadamard design with each letter repeated once and only once can exist for 2, 4 and 8 letters only. L.D. Baumert and Marshall Hall, Jr have found a design with four letters each repeated three times. Their design and the design on four letters each repeated once, found by J. Williamson, is the totality previously published.
Jennifer Seberry Wallis, Hadamard designs, Bulletin of the Australian Mathematical Society, 2, (1970), 45-54.