A.J. VAN DER POORTEN, A NOTE ON HADAMARD ROOTS OF RATIONAL FUNCTIONS, The Rocky Mountain Journal of Mathematics, Vol. 26, No. 3 (SUMMER 1996), pp. 1183-1197 ...

Hilbert’s 12th problem asked for novel analogues of the roots of unity, the building blocks for certain number systems. Now, over 100 years later, two mathematicians have produced them.