Bilusyak, N., Komarnyts’ka, L.I. and Ptashnik, B.I. 2002. Dirichlet-Type Problems for Systems of Partial Differential Equations Unresolved with Respect to the Highest Time Derivative. Ukrains’kyi Matematychnyi Zhurnal. 54, 12 (Dec. 2002), 1592-1602.