Keiichi Nakamura "On the isomonodromic deformation of certain Pfaffian systems associated to Appell's systems $\left( {F_2 } \right),\left( {F_3 } \right)$," Proceedings of the Japan Academy, Series A, Mathematical Sciences, Proc. Japan Acad. Ser. A Math. Sci. 64(8), 278-281, (1988)