Emerson, Edgar I. (1944). "A chart based on atomic numbers showing the electronic structure of the elements". Journal of Chemical Education. 21 (5): 254. Bibcode:1944JChEd..21..254E. doi:10.1021/ed021p254.
Emerson, Edgar I. (1944). "A chart based on atomic numbers showing the electronic structure of the elements". Journal of Chemical Education. 21 (5): 254. Bibcode:1944JChEd..21..254E. doi:10.1021/ed021p254.