| #5451 | OR-Spektrum. -- Berlin : Deutscher Gesellschaft für Operations Research, 1979-. -- ISSN 0171-6468 print. -- ISSN 1436-6304 online |
| #5452 | Oracle. -- Redwood Shores : Oracle Corporation, 1987-. -- ISSN 1065-3171 |
| #5453 | Organ für die Fortschritte des Eisenbahnwesens. -- Berlin : Springer, 1846-1920 |
| #5454 | Organic & biomolecular chemistry : An international journal of all areas of organic, physical organic and biomolecular organic chemistry. -- Cambridge : Royal Society of Chemistry, 2003-. -- ISSN 1477-0520 print. -- ISSN 1477-0539 online |
| #5455 | Organic electronics. -- Amsterdam : North-Holland, 2000-. -- ISSN 1566-1199 print. -- ISSN 1878-5530 online |
| #5456 | Organic letters. -- Columbus : American Chemical Society, 1999-. -- ISSN 1523-7060 print. -- ISSN 1523-7052 online |
| #5457 | Organic magnetic resonance. -- London : Heyden and Son, 1969-1984. -- ISSN 0030-4921 |
| #5458 | Organic process research & development. -- Washington : American Chemical Society, 1997-. -- ISSN 1083-6160 print. -- ISSN 1520-586X online |
| #5459 | Organometallics. -- Washington : American Chemical Society, 1982-. -- ISSN 0276-7333 print. -- ISSN 1520-6041 online |
| #5460 | Osaka Journal of Mathematics. -- Osaka : Osaka University, Department of Mathematics, 1964-. -- ISSN 0030-6126 |