Links
[1] https://hootsgo.org/?q=node/6291
[2] http://www.regentsprep.org/regents/math/geometry/GL1/indexGL1.htm
[3] http://www.regentsprep.org/regents/math/geometry/GL3/indexGL3.htm
[4] http://www.regentsprep.org/regents/math/geometry/MultipleChoiceReviewG/Locus.html