Earlier brief article by the same author: http://iopscience.iop.org/1538-4357/553/2/L97/fulltext http://iopscience.iop.org/1538-4357/553/2/L97/fulltext . I don'

Earlier brief article by the same author: http://iopscience.iop.org/1538-4357/553/2/L97/fulltext http://iopscience.iop.org/1538-4357/553/2/L97/fulltext . I don't know what's new in his latest; it seems to be qualitatively similar.