ERDOEL IN SUEDOSTASIEN UND SEINE VOLKSWIRTSCHAFTLICHE BEDEUTUNG FUER WESTEUROPA = PETROLE DU SUD-EST ASIATIQUE ET SON IMPORTANCE ECONOMIQUE POUR L'EUROPE OCCIDENTALEROLFF A.1978; VOLKSWIRTSCH. SCHR.; DEU; DA. 1978; NO 274; PP. 1-136; BIBL. 7 P.; 19 ILL.Serial Issue

BRAZILIAN IMPERIAL TOPAZ.ROLFF A.1971; LAPIDARY J.; USA; 1971(3), VOL. 24, NUM. 0012, P. 1556 A 1562Miscellaneous

PINK MINERALS FROM BRAZIL.ROLFF A.1971; LAPIDARY J.; USA; 1971(1), VOL. 24, NUM. 0010, P. 1300 A 1307Miscellaneous

THE GEOLOGIC ENVIRONMENT FOR EMERALD IN BRAZIL.ROLFF A.1970; LAPIDARY J.; USA; 1970(2), VOL. 23, NUM. 0011, P. 1488 A 1501Miscellaneous