• https://vtechworks.lib.vt.edu/items/fffe7f36-5539-49dc-918d-ef794c7156b0
• https://vtechworks.lib.vt.edu/items/ffffac5e-0c0f-4944-aed6-9895745af1ee
• https://vtechworks.lib.vt.edu/items/19092d92-3e10-4307-acc8-70a447901e21