Chowla, S. 1961. A Remarkable Solution of the Pel1an Equation X²-py² = -4, in the Case when p=1 |(4)| and the Class-Number of R(√p) is I. The Journal of the Indian Mathematical Society. 25, 1 (Mar. 1961), 43–46. DOI:https://doi.org/10.18311/jims/1961/16894.