Zahn, C. T. and Spees, A. A. (1938), «A Critical Analysis of the Classical Experiments on the Variation of Electron Mass» 7 ed. , Physical Review, 53: 511–521, Bibcode:1938PhRv...53..511Z, doi:10.1103/PhysRev.53.511 !CS1 manut: Nomes múltiplos: lista de autores (link)
Zahn, C. T. and Spees, A. A. (1938), «A Critical Analysis of the Classical Experiments on the Variation of Electron Mass» 7 ed. , Physical Review, 53: 511–521, Bibcode:1938PhRv...53..511Z, doi:10.1103/PhysRev.53.511 !CS1 manut: Nomes múltiplos: lista de autores (link)