| Name | Info | Provider | Link |
|---|---|---|---|
| Pain | free resource | MedlinePlus Health Information | https://medlineplus.gov/pain.html |
| free resource | Medicina Oral S.L. | http://www.medicinaoral.com/pubmed/medoralv17_i5_pe912.pdf | |
| free resource | PubMed Central | https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/22549694/ | |
| free resource | Europe PubMed Central | https://europepmc.org/abstract/MED/22549694 |