Pretty sure it's this paper: https://ieeexplore.ieee.org/document/1164317

That is Griffin-Lim, which matches the second mention but not the first. It's a fairly well known algorithm for reconstructing speech from spectrum, though I believe is largely superseded these days by vocoders based on neural techniques. (Actually I just checked and the original Tacotron paper cites Griffin-Lim; I do think newer neural TTS approaches have gone beyond it, however)