“…Recently, Dutkay, Hausserman, and Lai [10] generalized the result to higher dimensions, thus settling a long-standing conjecture proposed by Jorgensen and Pedersen. Meanwhile, many interesting spectral measures have been found (see, e.g., [1–7, 9, 12, 13, 15, 16, 23–26, 29] and the references therein for recent advances), but there are only a few classes.…”