• Enhancement ensures competitivenessPirk, KalleEstonian oil shale industry yearbook 20172018 / p. 5 : portr https://www.ester.ee/record=b5266187*est
• Research and development is the guarantee of oil shale's futurePirk, KalleEstonian oil shale industry yearbook 20162017 / p. 5 : portr https://www.ester.ee/record=b5266187*est
• The key for industrial development is ensuring a future workforcePirk, KalleEstonian oil shale industry yearbook 20182019 / p. 5 : portr https://www.ester.ee/record=b5266187*est