1. W. P. Champagne, Jr., On Finding Roots of Polynomials by Hook or by Crook, Master’s Thesis, Univ. of Texas, 1964.
2. Interval arithmetic in matrix computations. I;Hansen, Eldon;J. Soc. Indust. Appl. Math. Ser. B Numer. Anal.,1965
3. Interval arithmetic in matrix computations. II;Hansen, Eldon;SIAM J. Numer. Anal.,1967
4. Ray Boche, "Complex interval arithmetic with some applications," Lockheed Missiles and Space Company Report #4-22-66-1, 1966.