@misc{heerens_on_the_2003, 
author={Heerens, J., Schoedel, M.},
title={On the determination of crack tip opening angle, CTOA, using light microscopy and Delta5 measurement technique},
year={2003},
howpublished = {journal article},
note = {Heerens, J.; Schoedel, M.: On the determination of crack tip opening angle, CTOA, using light microscopy and Delta5 measurement technique. Engineering Fracture Mechanics. 2003. vol. 70, 417-426.}}