Individual: If_two_lines_are_parallel_a_perpendicular_line_to_one_of_them_is_also_perpendicular_to_the_other_one

http://www.inter2geo.eu/2008/ontology/GeoSkills#If_two_lines_are_parallel_a_perpendicular_line_to_one_of_them_is_also_perpendicular_to_the_other_one