T - Title
A - Author(s)
S - Source (link where you found the image)
L - License type (the Creative Commons license information)
"Creative Commons 10th Birthday Celebration San Francisco" by Timothy Vollmer is licensed under CC BY 4.0
TASL Details:
This work has been adapted from "Best practices for attribution" by CC Wiki which is licensed under a Creative Commons Attribution 4.0 License.
Once an OER has been selected, the next step is to determine how it is licensed and what permissions you have. Please note that open licenses do not replace copyright. Instead, they change the default of "all rights reserved" to "some rights reserved", the terms of which can vary:
Creative Commons Attribution (CC BY) is the most common open license. It grants the rights to use, adapt, and distribute the material as long as the author is attributed.
Creative Commons Attribute ShareAlike (CC BY-SA) grants the rights to use, adapt, and distribute the material as long as the author is attributed and derivative versions use the same license.
Creative Commons Attribution NonCommercial ShareAlike (CC BY-NC-SA) grants the right to use, adapt, and distribute non-commercially as long as the author is attributed and any derivative versions use the same license.
Creative Commons Attribution NoDerivs (CC BY-ND) allows for redistribution, commercial and non-commercial, as long as it is passed along unchanged, with credit to the author.
A full list of the types of open licenses is on the Creative Commons webpage. 
Note that public domain dedications are not Creative Commons licenses; instead, these licenses wave all rights reserved by copyright to place the work in the public domain. Attribution is often appreciated but not necessary.
Source: “How to attribute Creative Commons Photos” 
by Foter. Licensed under a CC-BY-SA 3.0 license