| Name | Info | Provider | Link |
|---|---|---|---|
| Tears | free resource | MedlinePlus Health Information | https://medlineplus.gov/tears.html |
| free resource | Molecular Vision | http://www.molvis.org/molvis/v25/934/ | |
| free resource | PubMed Central | https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/32038094/ | |
| free resource | Europe PubMed Central | https://europepmc.org/abstract/MED/32038094 |