Errata for paper: 
    Ellipse Detection Using Randomized Hough Transform May 20, 2002

Errata last updated: January 22, 2003

pg 10 Clarification for finding mx and my from the points X1 and X2.
    X1x refers to the x component of the point X1 and X1y refers to the
    y component. (I don't know what possessd me to use X for a point's name.)
    mx = (X1x + X2x) * 0.5
    my = (X1y + X2y) * 0.5
   

pg 10 Incorrect slope equation. 
    The slope should be:
    slope = (my - ty) / (mx - tx)