Variable Stars.- Variable Stars and Stellar Evolution (Invited Lecture).- On the Stability of the Light Curves of Galactic Cepheids.- On the Pulsation Amplitude of Cepheid Variables.- The Influence of an Axial Rotation and a Tidal Action on the Non-Radial Oscillations of a Star, with Reference to the ? Canis Majoris Stars.- An Atlas of Nova Delphini 1967.- Binary Stars.- Apsidal Motion in Close Binaries with Variable Orbital Period.- The Radius-Luminosity Relation in Eclipsing Binaries.- Kinematic Properties of Selected Visual Binaries.- Space Distribution and Motions of the Stars.- Gould's Belt (Invited Lecture).- On the Distribution of Stars in the Carina-Centaurus Region.- Conclusions on Galactic Kinematics from Proper Motions with Respect to Galaxies.- Interstellar Matter.- Molecules as Probes of the Interstellar Matter (Invited Lecture).- Molecules in the Widely Distributed Interstellar Clouds.- On the Homogeneity and the Kinetic Temperature of the Intercloud HI-Gas.- The Outer Spiral Structure of the Galaxy and the High-Velocity Clouds.- Very Long Baseline Interferometer Measurements of H2O Masers in Orion A, W49N, W30H and VY CMA (Abstract).- High Resolution Search for Interstellar Lithium.- Galactic Center.- Ionized Gas in the Direction of the Galactic Center I: Kinematics and Physical Conditions in the Nuclear Disk.- Results of Lunar Occultations of the Galactic Center Region in HI, OH and H2CO Lines and in the Nearby Continua.- A Model for the Galactic Center (Abstract).- Chemical Evolution of the Galaxy.- Diffusion of Elements in the Galaxy.- Narrow-Band Observations of Super-Metal-Rich Stars.- Fine Analytic Abundance Determination of Magellanic Cloud A-Supergiants and its Importance for the Discrimination of Theories for the Chemical Evolution of theGalaxy.- High Resolution Ultraviolet Stellar Spectra the Obtained with the Orbiting Stellar Spectrophotometer S 59.- Infrared Astronomy.- Infrared Astronomy (General Lecture).- Interpretation of Far Infrared Observations (Invited Lecture).- Infrared Techniques (Invited Lecture).- Infrared Photometry of Galactic HII Regions.- 8-13 ?m Spectrum of the Galactic Centre (Abstract).- Instruments.- High Speed Evaluation of Photographic Plates (Invited Lecture).- Analysis of Electronographic Images.- URSIES and the Bartol Coudé Observatory.- Three-Body Problem.- The Problem of Three Bodies (Invited Lecture).- Periodic Orbits of the Restricted Problem for Various Values of the Mass-Ratio.- On the Possibility of a Resonance Capture of the Asteroid Toro by the Earth.- Commensurable Mean Motions as a Tool in Solar System Dynamical Studies (Abstract).- Galactic Dynamics.- Galactic Models and Stellar Orbits (Invited Lecture).- The Gravitational N-Body Problem for Star Clusters (Invited Lecture).- A Comparative Study of Periodic Orbits (m
