1. https://tiedemann‐instruments.de/en/photoelasticity/principles/(15/07/2019)
2. https://classes.mst.edu/civeng2200/lessons/12/photoelasticity/index.html(14/7/2019)
3. On the communication of the structure of doubly refracting crystals to glass, muriate of soda, fluor spar and other substances, by mechanical compression and dilatation;Brewster D.;Phil Trans Roy Soc London,1816