1. S. Eilenberg and I. Niven,The Fundamental Theorem of Algebra for quaternions, Bull. Amer. Math. Soc., 50 (1944), pp. 246–248.
2. G. Gentili and D. C. Struppa,On the multiplicity of zeros of polynomials with quaternionic coefficients, Milan J. Math., 76 (2007), pp. 1–10.
3. G. Gentili, D. C. Struppa, and F. Vlacci,The fundamental theorem of algebra for Hamilton and Cayley numbers, Math. Z., 259 (2008), pp. 895–902.
4. G. Gentili and C. Stoppato,Zeros of regular functions and polynomials of a quaternionic variable, Michigan Math. J., 56 (2008), pp. 655–667.
5. B. Gordon and T. S. Motzkin,On the zeros of polynomials over division rings, Trans. Amer. Math. Soc., 116 (1965), pp. 218–226.