Screenshot of 4th Grade Science by USBE OER available under CC BY-NC-SA at:
http://www.ck12.org/user:dxrhac1vzxitzg9llnbhcnruzxjay2sxmi5vcmc./book/4th-Grade-Science/section/5.1/
Screenshot of 8th Grade Math by USBE OER available under CC BY-NC-SA at:
https://eq.uen.org/emedia/file/e9109a3d-709b-43ae-a44a-60375ea88048/1/8Ch5Textbook.pdf