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# Rule 2. Share your data online, with a permanent identifier.  Although many papers include URLs to give access to datasets, most become inaccessible within a few years (e.g., [Wren 2008]. Nothing really lasts forever, but you should make every effort to give your data identifiers that will be long-lasting. In general, your personal web site is unlikely to be a good option for long-term data storage (yet, in the very short run, putting your data on your site is better than doing nothing at all!). The best option for releasing your data with long-term guarantee is to deposit them in whatever data archive is the "go to" place for your field. The archive will assign an identifier such as a "handle" (hdl) or "digital object identifier" (doi), will assure that you have provided adequate documentation, and will manage the care and feeding of your data. If no such archive exists in your field, some generic online services will host your data and issue persistent identifiers (see Rule 8). Some of the pointers to repositories and  services are listed in the Appendix. [Wren 2008] "URL decay in MEDLINE—a 4-year follow-up study". Bioinformatics, Volume 24, Issue 11, pp. 1381-1385, 2008. doi: 10.1093/bioinformatics/btn127