“…Many spectral measures have been found, see, for example [1,3,7,8,9,10,11,12,15,22,25,27,33,34,36,35,38] and references therein. For a singular spectral measure, generally speaking, its spectrum containing 0 is not unique, see [2,8,24,21,21,27,31,32] and references therein. However, it is a big challenge to determine all the spectra for a given singular spectral measure.…”