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\bibitem{Lubk_etal2013} {\textquotedblleft}\textit{Transport of intensity phase retrieval of arbitrary wave fields including vortices}{\textquotedblright}. Lubk A, Guzzinati G, B{\"o}rrnert F, Verbeeck J, Physical review letters \textbf{111}, 173902 (2013).   http://doi.org/10.1103/PhysRevLett.111.173902

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