《國外數學名著係列(續一)(影印版)66:偏微分方程4(微局部分析和雙麯型方程)》主要內容：This volume of the Encyclopaedia contains two contributions．In the first Yu.V.Egorov gives an accomnt of microlocal analysis as a tool for investigating partial differemial equations．This 113ethod has become increasingly important in the theory．of Hamiltonian systems in recent years．

The second survey written by V.Ya．1vrii treats linear hyperbolic equations and systems．The author states necessary and sufficiient conditions for C∞-and L2-well-posedness and he studies the analogous pmhlem in the comext ofGevrey classes．He also describes,the latest results in，the theory of mixed problems for hyperbolic operators and concludes with a list of unsolved problems．

Both parts coyer recent research in two important fields,which before was scattered in numerous joumals．The book will hence be of immense value to graduate students and researchers in partial differential equationS and theoretical physics。