Elshafei, A. (1968). Product Performance Models PPM. The Institute of National Planning.
芝加哥风格引文Elshafei, Alwalid. Product Performance Models PPM. Cairo: The Institute of National Planning, 1968.
MLA引文Elshafei, Alwalid. Product Performance Models PPM. The Institute of National Planning, 1968.
警告：这些引文格式不一定是100％准确.