[1] A. Aziz and Q.G. Mohammad, Zero free regions for polynomials and some generalizations of Enestrom-Kakeya theorem, Canad. Math. Bull. 27 (1984), 265–272.
[2] A. Aziz and B.A. Zargar, Some extension of Enestrom-Kakeya theorem, Glasnik. Math. 31 (1996), 239–244.
[3] L. Brand, The roots of a quaternion, Amer. Math. Monthly 49 (1942), 519–520.
[4] N. Carney, R. Gardner, R. Keaton, and A. Powers, The Enestrom-Kakeya theorem of a quaternionic variable, J. Appl. Theory 250 (2020), Article 105325.
[5] G. Enestrom, Remarque sur un theoreme relatif aux racines de l'equation anxn+⋯+a0=0 ou tous les coefficients a sont reels et positifs, Tohoku. Math. J. 18 (1920), 34–36.
[6] C.F. Gauss, Beitrage zur theorie der algebraischen gleichungen, Abh. Ges. Wiss. Gottingen 4 (1850), 73–102.
[7] G. Gentili and C. Stoppato, Zeros of regular functions and polynomials of a quaternionic variable, Michigan. Math. 56 (2008), 655–667.
[8] G. Gentili and C.D. Struppa, A new theory of regular functions of a quaternionic variable, Adv. Math. 216 (2017), 279–301.
[9] N.K. Govil and Q.I. Rahman, On the Enestrom-Kakeya theorem, Tohoku Math. J. 20 (1968), 126–136.
[10] A. Hurwitz, Uber einen Satz des Harrn Kakeya, Tohoku Math. J. First Ser. 4 (1913–1914), 626–631.
[11] A. Joyal, G. Labelle and QI. Rahman, On the location of zeros of polynomials, Can. Math. Bull. 10 (1967), 53–63.
[12] S. Kakeya, On the limits of the roots of an algebraic equation with positive coefficient, Tohoku Math. J. 2 (1912–1913), 140–142.
[13] M. Marden, Geometry of polynomials, Math. Surveys, Amer. Math. Soc. 3 (1949).
[14] D. Tripathi, A note on Enestrom-Kakeya theorem for a polynomial with quaternionic variable, Arab. J. Math. 9 (2020), 707–714.