Sagan, A. ., Nowicki, S. ., Buczynski, R. ., Kowalczyk, M. ., & Szoplik, T. . (2003). Imaging phase objects with square-root, Foucault, and Hoffman real filters: a comparison. Applied Optics, 42(29), 5816-24. https://doi.org/10.1364/ao.42.005816 (Original work published 2003)