BEIJING, March 17 (Xinhua) -- China's publishing watchdog is planning action on teaching materials for primary and middle school students.

The campaign until May, will focus on grammatical and factual errors, improper printing and bundling as well as over-pricing, said a circular released Monday by the State Administration of Press, Publication, Radio, Film and Television.

Piracy and other irregular practices lead to errors that are becoming an issue for Chinese teachers and parents.

The administration also released details of typical cases in previous efforts. In Nanjing, capital of east China's Jiangsu Province, a local cultural group and a printing company were each fined 80,000 yuan (13,000 U.S. dollars) for printing and selling over 50,000 pirated publications. Two main ofenders were sentenced to three years and three years and four months in jail plus fines of up to 20,000 yuan for copyright infringement.