Doctor of sciences, professor, expert in organophosphorus chemistry. Prof. Tsvetkov investigated the methods for phosphorus-carbon bond formation, electronic effects of РIII- and РIV-substituents on reactivity of organometallic compounds (in particular, РН- and СН-acidity). This allowed to formulate the general dependence of electronic effects of EIII-substituents on the position of element in the Periodic table. Prof. Tsvetkov has also studied the phosphorous-containing linear analogues of crown-ethers. He has worked in INEOS RAS since 1955 in the laboratory of organophosphorus compounds. In 1979 he organized and headed the laboratory of organometallic compounds in the Institute of physiologically active compounds RAS.