| #2041 | Ontogenez. -- Moskva : Nauka, 1970-. -- ISSN 0475-1450 |
| #2042 | Operational research quarterly. -- Oxford : Pergamon Press, 1970-1977. -- ISSN 0030-3623 |
| #2043 | Optical engineering : the journal of SPIE - the International Society for Optical Engineering. -- Bellingham : Society of Photo-Optical Instrumentation Engineers, 1972-. -- ISSN 0091-3286 |
| #2044 | Optics letters. -- Washington : Optical Society of America, 1977-. -- ISSN 0146-9592 print. -- ISSN 1539-4794 online |
| #2045 | Optika i spektroskopija. -- Leningrad : Nauka, 1956-. -- ISSN 0030-4034 |
| #2046 | Optimization. -- Yverdon : Akademie-Verlag, 1977-. -- ISSN 0233-1934 |
| #2047 | Optoelektronika i poluprovodnikovaja technika. -- Kijev : Naukova dumka. -- ISSN 0233-7577 |
| #2048 | Orbis litterarum. -- Copenhagen : Munksgaard, 1943-. -- ISSN 0105-7510 print. -- ISSN 1600-0730 online |
| #2049 | Organizacija i planirovanije otraslej narodnogo chozjajstva. -- Kiev : Izdatel´stvo Kievskogo universiteta, 1965-. -- ISSN 0131-0151 |
| #2050 | Organon. -- Warszawa : Instytut Historii Nauki Polskiej Akademii Nauk, 1964-. -- ISSN 0078-6500 |