“…• a more operator-theoretic line in the Faddeev-Minlos spirit, developed from the mid 1980's to the recent years by Minlos (also in collaboration with Menlikov, Mogilner, and Shermatov) [176,185,186,169,170,177,215,178,179,180,181,182], with also recent contributions by Yoshitomi [253], by Michelangeli and Ottolini [172,173], and by Becker, Michelangeli, and Ottolini [30]; • a line exploiting quadratic forms methods, initiated at the end of the 1980's by Dell'Antonio, Figari, and Teta and mainly developed in the following decades by an Italian community [230,74,75,101,64,175,66,65,29,174,27], with also recent contributions by Moser and Seiringer [187,188]; • a side line by Pavlov and his school [154,168], retaining the same ideas, but aimed at rigorously constructing variants of the formal Hamiltonian (6.5) for particles with spin, and a spin-spin contact interaction; • a further line where (three-dimensional) three-body Hamiltonians with zerorange interactions are constructed as rigorous limits, in the resolvent sense, of ordinary Schrödinger operators with potentials that scale up to a delta-like profile -an idea discussed first by Albeverio, Høegh-Krohn, and Wu [10] in the early 1980's, and subsequently by Dimock and Rajeev [83] in the planar analogue (more recently, one-and two-dimensional counterpart results have been established in [26,126,125]).…”