BT BQ 66b(27) :הא מ^י^לתא קשאי בי רבה לרב יוסף תרתין ועשרין שנין ולא אשתנאי‏ : this matter was difficult for PN for twenty-two years in the school of PN2 and was not clarified
See the entire entry for qšy vb. to be difficult