H. F. Unger

Percussive drilling with independent rotation

H. F. Unger, R. R. Fumanti, 1972 .

Drillability determination. A drillability index for percussion drills : 12F. US BUR. MINES RI 8073, 1975, 20P

H. F. Unger, S. Tandanand, S. Tandanand, 1976 .