Synthetic fuel Ruhr Area. In 1937, the four central Germany lignite coal plants at Böhlen, Leuna, Magdeburg/Rothensee, and Zeitz, along with the Ruhr Area bituminous coal plant at Scholven/Buer, had produced of fuel. Four new hydrogenation plants () were subsequently erected at Bottrop-Welheim (which used "Bituminous coal tar pitch"), Gelsenkirchen (Nordstern), Pölitz, and, at 200,000 tons/yr Wesseling. Nordstern and Pölitz/Stettin used bituminous coal, as did the new Blechhammer plants. Heydebreck synthesized food oil, which was tested on concentration camp prisoners. The Geilenberg Special Staff was using 350,000 mostly foreign forced laborers to reconstruct the bombed synthetic oil plants, and, in an emergency
Interlanguage fossilization 1) why fossilization occurs, 2) the precipitating conditions, 3) what kind of linguistic material is likely to be fossilized, and 4) what type of learners are more prone to fossilize. However, there has been almost no investigation by SLA theorists on the possibilities of preventing or overcoming fossilization, and little explanation related to those adult second language learners who overcome one or more "areas of stability" in interlanguage—those learners whose interlanguage does not fossilize, and who reach a high level of proficiency in the second language. One factor of obvious relevance is motivation, and studies have been conducted regarding motivation