Invited Discourses -- A. Exploring the Moon -- B. Couches extérieures et structure interne des étoiles -- C. Radio Galaxies and Quasars, I -- D. Radio Galaxies and Quasars, II -- Joint Discussions -- A. New Techniques in Space Astronomy -- Recent Techniques in Solar Optical Astronomy from Space -- Ultraviolet Astronomy -- New Techniques in X-Ray Astronomy -- Solar and Interplanetary Magnetic Fields and Plasmas -- Infrared Astronomy -- Some Problems and Instrumental Features of Sub-millimeter Astronomy -- New Techniques in Space Radio-astronomy -- B. X-Ray Astronomy -- Surveys of X-Ray Sources -- Recent Results on Extragalactic Cosmic X-Ray Sources from Rocket and Balloon Flights -- A Cosmic X-Ray Survey in the Southern Hemisphere -- Results from Detailed Studies of X-Ray Sources -- The X-Ray Spectra of Cygnus XR-1 and the Crab Nebula -- Optical and Radio Information -- Theoretical Review -- X-Rays Radiation of a Neutron Star as a Result of Gas Accretion -- The Cosmic X-Ray Background -- C. The Lithium Problem -- The Occurrence of Lithium in Stars -- Evidence for Lithium Destruction and Synthesis in Main-Sequence and Subgiant Stars of about Solar Mass -- Observations of Beryllium in Stars -- Lithium Observations in the Sun -- On the Lithium Abundance in Sunspots and the Undisturbed Solar Atmosphere -- The Formation of Li, Be, B Isotopes by the Spallation of CNO -- What can we learn from Li and Be Stellar Observations? -- The Mixing of Lithium -- D. Modem Problems of Fundamental A strömetry -- The AGK3, SRS and Related Projects -- Recent Work on Fundamental Astrometry in the U.S.S.R -- Meridian Observations at Santiago, Chile -- Preliminary Results of the Determination of Absolute Proper Motions of Stars referred to Galaxies -- Desiderata for FK5 -- Precession and Galactic Rotation on the Basis of Various Proper Motion Systems -- The Relationships between Various Techniques for obtaining Proper Motions -- The Place of Accurate Proper Motions in Galactic Research -- Études sur l'emploi de Recouvrements de Plaques pour l'établissement de Catalogues Photographiques -- The Overlap Approach toward the Derivation of Photographic Stellar Coordinates -- Report on Overlap Methods in Photographic Astrometry -- Relative Star Positions from Overlapping Photographic Plates -- E. Extragalactic Radio Sources -- Optical Studies of Extragalactic Radio Sources -- Burbidge Optical Spectra of Extragalactic Radio Sources -- Radio Observations of Angular Structure -- Radio-Source Spectra and their Time Variations -- Infrared Observations of QSS -- Millimetre-Wave Observations -- The Nature of the Red-Shifts in Quasi-Stellar Objects -- Theories proposed to explain Quasi-Stellar Objects and Radio Galaxies -- A Cosmological Interpretation of the Absorption-Line Spectra of QSO -- The Evolution of Quasi-Stellar Sources and Radio Galaxies -- The Magnetodynamic Model of Quasars -- A Rotating Disk Model for a Quasar -- Shorter Contributions -- F. Close Binaries and Stellar Evolution -- Opening Remarks -- On the Origin of the Algol Systems -- The Evolution of Close Binaries and the Formation of the Wolf-Rayet Stars -- White Dwarfs in Close Binary Systems -- Arguments indicating that Ap and Am Stars are Evolved Spectroscopic Binaries -- Investigation of Possible Abundance Anomalies in Close Binaries of Spectral Types A0-A2 & F5-F6 -- The Evolution of Close Binaries and the Am Stars -- Origin of Binaries from a Consideration of Angular Momentum -- The Origin and Early Evolution of Close Binary Stars -- The Structure of W Ursae Majoris Systems -- Comments -- A Model for the Nova Outburst -- Concluding Remarks -- Special Meetings -- A. Lunar Probes -- A Description of the Lunar Orbiter Spacecraft -- Photographic Results of the Lunar Orbiter Program -- B. Coordination of Solar Observations made at Ground-Based Observatories and with Space Vehicles -- The Need of Ground-Correlated High-Resolution Space Observations in the Visible -- Space Observations Needed for Improving Our Knowledge of Solar Flares -- Space Observations of Flare Sprays and Related Surge Phenomena -- The Needs and Requirements from the Standpoint of the Ultraviolet Solar Observations -- Hard Solar X-ray Bursts -- Solar Gamma Rays and their Correlation with Space and Ground-Based Observations -- The Coordination of Ground-Based and Space Observations: Summary.