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"The Power of Non-violence: The Enduring Legacy of Richard Gregg" by John Wooding is a biography that explores the life of Richard Gregg, an American lawyer who became a disciple of Mahatma Gandhi and made significant contributions to the American civil rights movement. The book also delves into the personal journey of the author, an Englishman, as he examines his own relationship with his father through his work on Gregg. The biography highlights Gregg's time in India, his involvement in the Indian independence movement, and his writings on non-violence and voluntary simplicity. Overall, the book offers a compelling portrait of a quiet and dissenting radical whose ideas remain relevant today. [Extracted from the article]

Multiple wavelength phase shifting interferometry is widely used to extend the unambiguous range (UR) beyond that of a single wavelength. Towards this end, many algorithms have been developed to calculate the optical path difference (OPD) from the phase measurements of multiple wavelengths. These algorithms fail when phase error exceeds a specific threshold. In this paper, we examine this failure condition. We introduce a "phase-space" view of multi-wavelength algorithms and demonstrate how this view may be used to understand an algorithm's robustness to phase measurement error. In particular, we show that the robustness of the synthetic wavelength algorithm deteriorates near the edges of its UR. We show that the robustness of de Groot's extended range algorithm [Appl. Opt.33, 5948 (1994)APOPAI0003-693510.1364/AO.33.005948] depends on both wavelength and OPD in a non-trivial manner. Further, we demonstrate that the algorithm developed by Houairi and Cassaing (HC) [J. Opt. Soc. Am. A26, 2503 (2009)JOAOD60740-323210.1364/JOSAA.26.002503] results in uniform robustness across the entire UR. Finally, we explore the effect that wavelength error has on the robustness of the HC algorithm.