Newton's method, presented at [url]http://mathpages.com/home/kmath546/kmath546.htm[/url], appears to be missing some lines on the diagram that is representing the construction.
Newton's method, presented at [url]http://www2.washjeff.edu/users/mwoltermann/Dorrie/45.pdf[/url], uses the phrase "Mark off on the diagonals from OP = sqrt(OA*OC)" on page 3 where it is telling how to construct the two possible orientations of a parabola through 4 points and it is not clear to me what that phrase means.