The Austrian physicist Erwin Schroedinger (1887-1961) incorporatd the wave nature of the electron suggested by de Broglie into the theory of the hydrogen atom, substituting standing waves to describe the likely whereabouts of the electron in favor of the Bohr-Sommerfeld orbits. These solutions to the Schrodinger wave equation are discrete in that they depend on an integral number of wavelengths to occur in a possible orbit so as not to cancel each other out. Two such electronic states, in which the hydrogen atom is in a stable position, are shown on the Swedish stamp.