Niels Bohr

The quantum postulate and the recent development of atomic theory

The Theory of Spectra and Atomic Constitution: Three Essays

Quantum Theory (Concise Edition)

Quantum Theory: The Origin and Development of the Quantum Theory by Max Planck and The Quantum Theory of Line Spectra by Niels Bohr

On the quantum theory of radiation and the structure of the atom

On the effect of electric and magnetic fields on spectral lines

Paarläufe der Wissenschaft