Heistand, Robert N. The Fischer Assay, standard method?(PDF). San Francisco: Symposium on oil shale, tar sands, and related materials — production and utilization of synfuels. 1976 [2008-08-18]. (原始内容(PDF)存档于2012-02-11).
Heistand, Robert N. The Fischer Assay, standard method?(PDF). San Francisco: Symposium on oil shale, tar sands, and related materials — production and utilization of synfuels. 1976 [2008-08-18]. (原始内容(PDF)存档于2012-02-11).