| #541 | Priroda. -- Moskva : Nauka, 1912-. -- ISSN 0032-874X |
| #542 | Priroda. -- Sofia : Balgarska Akademija na Naukite, 1952-. -- ISSN 0032-8731 |
| #543 | Proceedings. -- London : Royal Society, 1990-1996. -- ISSN 0962-8444 |
| #544 | Proceedings in print. -- [Arlington] : [Proceedings in Print], 1964-1997. -- ISSN 0032-9568 |
| #545 | Proceedings of the Academy of Natural Sciences of Philadelphia. -- Philadelphia : Academy of Natural Sciences of Philadelphia, 1841-. -- ISSN 0097-3157 print. -- ISSN 1938-5293 online |
| #546 | Proceedings of the Bournemouth Natural Science Society. -- Bournemouth : Bournemouth Natural Science Society, 1922-. -- ISSN 0962-5364 |
| #547 | Proceedings of the Indian National Scientific Academy, Pt. A. Physical sciences. -- New Delhi : Indian National Sceince Academy, 1970-. -- ISSN 0370-0046 |
| #548 | Proceedings of the Indiana Academy of Science. -- Indianapolis : Indiana Acad. of Science, 1891-. -- ISSN 0073-6767 |
| #549 | Proceedings of the Iowa Academy of Science. -- Des moines : Iowa Academy of Science, 1889-1987. -- ISSN 0085-2236 |
| #550 | Proceedings of the Japan Academy, Series B, Physical and biological sciences. -- Tokyo : Japan Academy, 1977-. -- ISSN 0386-2208 |