This volume contains three articles: "Asymptotic methods in the theory of ordinary differential equations" b'y V. F. Butuzov, A. B. Vasil'eva, and M. V. Fedoryuk, "The theory of best ap proximation in Dormed linear spaces" by A. L. Garkavi, and "Dy namical systems with invariant measure" by A. 'VI. Vershik and S. A. Yuzvinskii. The first article surveys the literature on linear and non linear singular asymptotic problems, in particular, differential equations with a small parameter. The period covered by the survey is primarily 1962-1967. The second article is devoted to the problem of existence, characterization, and uniqueness of best approximations in Banach spaces. One of the chapters also deals with the problem of the convergence of positive operators, inasmuch as the ideas and methods of this theory are close to those of the theory of best ap proximation. The survey covers the literature of the decade 1958-1967. The third article is devoted to a comparatively new and rapid ly growing branch of mathematics which is closely related to many classical and modern mathematical disciplines. A survey is given of results in entropy theory, classical dynamic systems, ergodic theorems, etc. The results surveyed were primarily published during the period 1956-1967.

A collection of survey papers on the 50th anniversary of the institute.

Collections of this sort are a regular publication feature of the Laboratory of Mathemati cal Geology of the Order of Lenin V. A. Steklov Mathematical Institute of the Academy of Sci ences of the USSR. In the future it is intended that further collections and monographs reflect ing the activity of the Laboratory be issued. In this present collection, in addition to workers of the Laboratory of Mathematical Geology, specialists of both Russia and many foreign countries participated. This has permit ted us to display the general level of mathematization of geology in 1966. In order to enhance the overall view, the editors have included a section "Chronicle and Bibliography" in which in formation is given on the most important actions relating to mathematization of geology taking place in 1965 and the first half of 1966, and which includes a bibliography on two-dimensional regressions having great practical value in geology but little known to us in the Soviet Union.