| #951 | OEM off - highway. -- Fort Atkinson : Johnson Hill Press, 1990-. -- ISSN 1048-3039 print. -- ISSN 2158-7094 online |
| #952 | OG. -- Emmaus : Rodale, 1988-. -- ISSN 1536-108X |
| #953 | Ochrana rostlin. -- Praha : UZPI, 1965-1997. -- ISSN 0862-8645 |
| #954 | Ochrona Roślin. -- Kraków : Plantpress, 1960-. -- ISSN 0029-8239 |
| #955 | Oil World Weekly. -- Hamburg : ISTA Milke, 1958-. -- ISSN 0029-8700 |
| #956 | Onderstepoort journal of veterinary research. -- : Department of Agriculture and Water Supply, 1951-. -- ISSN 0030-2465 |
| #957 | Organic Agriculture : Journal of the International Society of Organic Agriculture Research. -- Dordrecht : Springer Netherlands, 2011-. -- ISSN 1879-4238 |
| #958 | Organic gardening. -- Emmaus : Rodale Press, 1988-2001. -- ISSN 0897-3792 |
| #959 | Organisms diversity & evolution. -- Jena : Elsevier, 2001-. -- ISSN 1439-6092 print. -- ISSN 1618-1077 online |
| #960 | Osnabrücker Schwarzbuntzucht. -- Melle : Osnabrücker Herdbuch - Gesellschaft e.V. |