Thank you for this amazingly informative article. I hardly like to mention that, in equation (4) above, where you have given the equations of the foci of an ellipse, the second set of co-ordinates should refer to F2, and not F3 as listed. I am sure that this is just a typing error and does not detract from the excellence of this treatise.

Sorry for making such a minute correction to this spendid article.

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