PEDERSEN, Steen; WANG, Yang. Universal spectra, universal tiling sets and the spectral set conjecture. Mathematica Scandinavica, Berkeley, CA, United States, v. 88, n. 2, p. 246–256, 2001. DOI: 10.7146/math.scand.a-14325. Disponível em: https://journals.msp.org/mscand/article/view/880. Acesso em: 24 jul. 2026.