https://acikders.ankara.edu.tr/pluginfile.php/113762/mod_url/intro/4-AYAK-AYAK%20B%C4%B0LE%C4%9E%C4%B0-KAS%20DE%C4%9EERLEND%C4%B0RMES%C4%B0%2C%20NEH%20VE%20TESTLER.pdf