[ابو بيشو]

I don't know on whose authority you say that .
لا يمكن وضع حرف الجر on فى نهاية هذه الجمله لا يمكن ان نقول
I don't know whose authority you say that on.
كذلك هذه الجمله
He doesn't say by what reasoning he arrived at that conclusion.
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He played quite a good game.= He played a quite good game.
That is rather a valuable picture.=That is a rather valuable picture.