1. S. Epstein, H. C. Cross, E. C. Groesbeck, and I. J. Wymore, “Observations on the iron-nitrogen system,” J. Res. (U.S. Nat. Bur. Stand.), 3, 1005 – 1027 (1929).
2. G. Hägg, “The iron-nitrogen system,” Nova Acta Reg. Soc. Sci. Upsaliensis, 4(7(1)), 6 – 22 (1928).
3. O. Eisenhut and E. Kaupp, “The system iron-nitrogen from x-ray diffraction investigations,” Z. Elektrochem., 36(6), 392 – 404 (1930).
4. W. Köster, “On the question of nitrogen in technical iron,” Archiv. Eisenhiitten, 3(10), 637 – 648 (1930).
5. E. Lehrer, “Magnetic investigation of the system iron-nitrogen,” Z. Elektrochem., 36(7), 460 – 473 (1930).