In this paper, we show that a connected graph with smallest eigenvalue at least -3 and large enough minimal degree is 2-integrable. This result generalizes a 1977 result of Hoffman for connected graphs with smallest eigenvalue at least -2.
@article{arxiv.1804.00369,
title = {On graphs with smallest eigenvalue at least -3 and their lattices},
author = {Jack H. Koolen and Jae Young Yang and Qianqian Yang},
journal= {arXiv preprint arXiv:1804.00369},
year = {2018}
}