Chowla, S. (1961) “A Remarkable Solution of the Pel1an Equation X<sup>2</sup>-py<sup>2</sup> = -4, in the Case when p=1 |(4)| and the Class-Number of R(&#8730;p) is I”, The Journal of the Indian Mathematical Society, 25(1), pp. 43–46. doi: 10.18311/jims/1961/16894.