[2] Bãdulescu C., Crãescu I., Traistã E., Ionescu Cl., 1993 Concerns about the recovery of some useful mineral substances from the ashes resulting from the combustion of coal (in romanian), Scientific communication session of Univ. Petroşani, vol. XXVI, p.37.
[4] Bãdulescu C., Traistã E., 1996 The Administration of Barren Gangue and Flying Ashes Spoil Dumps From Jiu-Valley, România, 3rd Conference on Environment and Mineral Processing, Ostrava, p.141.
[5] Bãdulescu C., Traistã E., Ionescu Cl., 1995 Precious Metal Extraction From the Ash Resulted From Jiu-Valley Bituminous Coal Burning, 6th Balkan Conference on Mineral Processing, Ohrid, Macedonia, p.87.
[9] Crãescu I., Traistã E., Ionescu Cl., Cristea G., 1996 Establishing the content of microelements from the coal ash extracted at the mining units in the Jiu Valley (in romanian), Contract no. 2/1996.