Srinivasa Rao, K., and V. Rajeswari. “Classification of the Polynomial Zeros of the 3-$j$ and the 6-$j$ Coefficients”. Revista Mexicana De Física, vol. 31, no. 4, Jan. 1984, pp. 575-99, https://rmf.smf.mx/ojs/index.php/rmf/article/view/1335.