1. Methane Roof Layers;Bakke;Min. Power (Gt. Britain) Safety Mines Res. Estab., Res. Rept.,1960
2. Berg- und Hüttenmännische;Meerbach;Monatshefte,1963
3. Formation and flammability of stratified methane-air mixtures;Perlee;U.S. Bur. Mines, Rept. Invest.,1964