Masayuki Sato Noriaki Ohba Hiromi Watanabe Shozo Saito Stick diagram extraction program SKELETON. 318-321 1988 ICCAD https://doi.org/10.1109/ICCAD.1988.122519 https://doi.ieeecomputersociety.org/10.1109/ICCAD.1988.122519 conf/iccad/1988 db/conf/iccad/iccad1988.html#SatoOWS88