Dave A. Voss Abdul-Qayyum M. Khaliq Time-stepping algorithms for semidiscretized linear parabolic PDEs based on rational approximants with distinct real poles. 353-363 1996 6 Adv. Comput. Math. 1 http://dx.doi.org/10.1007/BF02127713 db/journals/adcm/adcm6.html#VossK96