1. 2) H. SCHENCK and HENGLER: Arch Eisenhuten. 5 (1932), 209.
2. 3) BENRDICCKS and LOFQUIST: Z.V.D.I. (1927), 1,576.
3. 4) OBERHOFFER ETC.: Stahl u. Eisen 47 (1927), 1,540.
4. 15) EILENDER ETC.: Met. Ind. July, (1938), 60.
5. 6) GIOLITTI: Cementation of Iron and Steel 160 p.