[PER] of which one side appears to be orange

"There are three men on a train. One of them is an economist and one of them is a logician and one of them is a mathematician. And they have just crossed the border into Holland and they see an orange sheep standing in a field from the window of the train.

And the economist says, "Look, the sheep in Holland are orange."

And the logician says, "No. There are sheep in Holland of which one at least is orange."

And the mathematician says, "No. There is at least one sheep in Holland, of which one side appears to be orange."

Because economists are not real scientists, and because logicians think more clearly, but mathematicians are best."

всё оттуда же, с некоторыми (уместными) девиациями.