author: paul erdős

This book will surely arouse the interest of the student and the teacher alike. Until his death in 1996, Professor Paul Erdös was one of the most prolific mathematicians ever, publishing close to 1,500 papers.

... n . J. Spencer [ 9 ] , took 20 x 20 Hadamard matrix and using the correspondence of Williamson [ 11 ] constructed a 19 × 19 , ( 0 , 1 ) -matrix . Altering it slightly to destroy the symmetry , he achieved an extremal exact cover of - 740-