5 whys to explore the cause and effect relationship . Tootmistehnika ja -süsteemide terminibaas. Estonian Language Institute, Sõnaveeb 2026.
https://sonaveeb.ee/search/unif//tts/5%20whys%20to%20explore%20the%20cause%20and%20effect%20relationship/1/eng (07.08.2026)