1. (1962) Protodyakonov M Mechanical properties and drillability of rocks. In: Proceedings of the Fifth Symposium on Rock Mechanics. University of Minnesota, Minneapolis, MN, pp 103–118
2. Paone J, Madson D, Bruce WE (1969) Drillability studies: laboratory percussive drilling. Bureau of Mines, Twin Cities, MN (USA), Twin Cities Mining Research Center
3. Tandanand S, Unger HF (1975) Drillability determination: a drillability index for percussion drills, vol 8073. US Dept. of the Interior, Bureau of Mines
4. Paithankar A, Misra G (1976) A critical appraisal of the Protodyakonov index. Int J Rock Mech Min Sci 13(8):249–251
5. Rabia H (1985) Oilwell drilling engineering: principles and practise, . Graham & Tromtman, Huddersfield, England, 322 s