HARD AND MASSIVE OVERLYING STRATA
hard and massive strata
hard kaolin (kaolinite) in coal measures strata
medium hard rock strata
shallow depth hard overlying strata
Hard Roof and Hard Coal
Hard Roof and Hard Floor
hard-soft-hard sandwich media
20 m VERY THICK AND MEDIUM HARD SEAM
3 channels hard cholecystoscope
A Good Man Is Hard to Find