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I'm still waiting on you to cite your source for the allegation that whether something is convex or concave depends on the perspective of the observer (or whether it's outward or inward, or however you want to phrase it).  My position is that there is no ambiguity in describing it as simply ""convex.""  I don't think the Turner and Godfray articles are correct, and just use a different phrasing.  I'm alleging that they're just outright wrong. -   "