• High temperature diffusion of halogens and alkali metals into polyparaphenyleneGolovtsov, Igor; Öpik, AndresSynthetic metals1999 / p. 463-464: ill
• High temperature diffusion of halogens and alkali metals into polyparaphenyleneGolovtsov, Igor; Öpik, AndresInternational Conference on Science and Technology of Synthetic Metals : ICSM'98 : July 12-18, 1998, Montpellier, France : book of abstracts1998 / p. 204 https://www.sciencedirect.com/science/article/abs/pii/S0379677998012004
• The conductivity mechanism of polyparapenylene, doped with halogens and alkali metalsÖpik, Andres; Golovtsov, Igor; Lobanov, A.; Kerm, KarinProceedings of the International Conference on Synthetic Metals, Göteborg, 19921992 / p. 311
• Utilization of high calcium oxide and alkali metal content fuel at the thermal power plantsOts, ArvoLow-grade fuels. Helsinki, Finland, June 12-16 1989. Vol. 21990 / p. 73-90: ill
• Utilization of high calcium oxide and alkali metal contentfuel at the thermal power plantsOts, A.A.Горючие сланцы1990 / 3-4, p. 321-332: ill