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See also the BAMS paper Perturbations, deformations, and variations (and near-misses") in geometry, physics, and number theory by Barry Mazur, in particular, Sections 4 and 5.
See also the BAMS paper Perturbations, deformations, and variations (and near-misses") in geometry, physics, and number theory by Barry Mazur, in particular, Sections 4 and 5.