  I. Introduction
  II. Electrons at the Fermi level
  III. Conductance quantization of a quantum point contact
  IV. Optical analogue of the conductance quantization
  V. Classical electron focusing
  VI. Electron focusing as a transmission problem
  VII. Coherent electron focusing (Experiment, Skipping orbits and magnetic
edge states, Mode-interference and coherent electron focusing)
  VIII. Other mode-interference phenomena
