Nuclear Vibrations and Force Constants.- Some Aspects of the Quantumchemical Interpretation of Integrated Intensities of Infrared Absorption Bands.- The Orbital Concept as a Foundation for Photoelectron Spectroscopy.- The Equivalent Bond Orbital Model and the Interpretation of PE Spectra.- Through-space and Through-bond Interactions as Mirrored in Photoelectron Spectra.- Penning Ionization - The Outer Shape of Molecules.- The Meaning and Distribution of Atomic Charges in Molecules.- Electron Spectroscopy for Chemical Analysis (ESCA) - Basic Features and Their Model Description.- Experimental Momentum-Space Chemistry by (e, 2e) Spectroscopy.- Theoretical Parameters of NMR Spectroscopy.- Theoretical Approaches to ESR Spectroscopy.- Rovibrational Averaging of Molecular Electronic Properties.- Properties of Molecules in Excited States.- Semiclassical Interpretation of Intramolecular Interactions.- The Analysis of Potential Energy Surfaces in Terms of the Diabatic Surface Model.