| Name | Info | Provider | Link |
|---|---|---|---|
| subscription/membership/fee required | Ovid Technologies, Inc. | http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=21533741.ui | |
| subscription/membership/fee required | Springer | https://link.springer.com/10.1007/s10072-011-0528-1 |