Some official information on Dongping 东平 district has been published online (short overviews):
http://www.sddongping.gov.cn/main_wenhua.asp
http://www.zgsf.com.cn/cgi-bin/view.cgi?forum=87&topic=3
http://bbs.people.com.cn/bbs/ReadFile?whichfile=443&typeid=79

A number of articles by Zhang Zong 张总 are available at Guoxue.com:
http://www.guoxue.com/discord/zz/ml.htm

An article by Xu Qing 徐清 "试论平阴三山摩崖与各地摩崖刻经的关系" was published in Beijing wenbo (北京文博 2000.4):
http://www.bjww.gov.cn/bjwenbo_page/bjwb_4/bjwb4_8_3.htm