What is today known as the Bohr-van Leeuwen theorem was discovered by Niels Bohr in 1911 in his doctoral dissertation[REF] and was later rediscovered by Hendrika Johanna van Leeuwen in her doctoral thesis in 1919 [REF].
The significance of this discovery is that classical physics does not allow for such things as paramagnetism, diamagnetism and ferromagnetism and thus quantum physics are needed to explain the magnetic events [REF].