sphinx-like

See: mysterious
References in classic literature ?
Franz did not doubt that these plans were the same concerning which the count had dropped a few words in the grotto of Monte Cristo, and while the Count was speaking the young man watched him closely, hoping to read something of his purpose in his face, but his countenance was inscrutable especially when, as in the present case, it was veiled in a sphinx-like smile.
The drunken and whorish Mauricia la Dura, from Fortunata y Jacinta (1886-87), has sphinx-like characteristics (686); in the novel El Abuelo (1897), the esfinges figure prominently in the description of a dark and sinister night, a night of would-be suicides (".
Kolchin owes his notion of a sphinx-like South to the late David Potter, whose comparative work--often pursued at the international level--he groups with that of C.
On the Star Wars absurdity ($55 billion and counting), Bradley has maintained a sphinx-like silence.