| Name | Info | Provider | Link |
|---|---|---|---|
| Gas | free resource | MedlinePlus Health Information | https://medlineplus.gov/gas.html |
| subscription/membership/fee required | Ovid Technologies, Inc. | http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=19120881.ui | |
| subscription/membership/fee required | Wiley | https://doi.org/10.1111/j.1440-1746.2008.05708.x |