Background Research

Cost and effectiveness
http://www.angieslist.com/articles/can-custom-orthotics-relieve-foot-pain.htm
http://www.nytimes.com/2006/06/22/fashion/thursdaystyles/22Fitness.html?pagewanted=all&_r=0

Over the counter (OTC) vs. custom 
http://articles.chicagotribune.com/2011-03-30/a-z/sc-health-0330-orthotics-20110330_1_orthotics-physical-therapist-foot-pain
http://www.footeducation.com/foot-and-ankle-basics/foot-and-ankle-medical-supplies/pre-fabricated-over-the-counter-orthotics-insert/prefabricated-over-the-counter-orthotics-versus-custom-orthotics/
http://www.complex.com/sneakers/2013/12/comprehensive-guide-choosing-best-otc-orthotics

Flat feet and pronation 
http://www.webmd.com/children/excessive-pronation

Uses and Diagnosis
http://orthoinfo.aaos.org/topic.cfm?topic=a00172 

Orthotics
http://www.scheckandsiress.com/documents/UCBL-JM.pdf

https://www.delatorreop.com/product/foot-orthotic-orthopedic-ucbl/

Plastics
http://www.protoparadigm.com/news-updates/the-difference-between-abs-and-pla-for-3d-printing/