Stupel, Moshe, and David Fraivert. “The Properties of Straight Lines That Issue from the Point of Intersection of the Diagonals of a Trapezoid, and Are Perpendicular to Its Sides”. Journal of Progressive Research in Mathematics 5, no. 4 (October 27, 2015): 618-623. Accessed May 18, 2024. http://scitecresearch.com/journals/index.php/jprm/article/view/437.