He has written and edited 30 books, including three college textbooks. They stressed ungraded curricula, modern textbooks, and new examination systems. The NCTB is responsible for developing curriculum and publishing standard textbooks. The play is frequently anthologized in American literature textbooks. This is outlined in many introductory textbooks in evolutionary psychology. It includes a number of periodicals, textbooks, dictionaries and audio-visual materials. Not all math textbooks and papers are consistent in this respect throughout. Long's free textbooks, school-building program, and school busing improved and expanded the public education system. The authorities removed Quranic passages that were deemed too violent from religion education textbooks. Some high-school-level discrete mathematics textbooks have appeared as well. Greek and French classes make use of supplemental materials that are more like traditional textbooks. It is similar to the descriptions of factorials found in mathematics textbooks. There is a general lack of facilities, equipment, qualified teachers, textbooks and other resources. Interior design courses were established, requiring the publication of textbooks and reference sources. It is commonly found printed in the opening pages of school textbooks and calendars.