He published over 150 research articles and 5 books during his life.
He has published over 150 books in the past 25 years.
In total, he published over 30 books, most of which fall into five categories.
As of February 2013, he has published over 150 books.
During his career he published over 400 research articles and 8 books.
He has published over 80 books and 400 academic papers.
By 1980 he had published over 100 books for children in nearly 30 languages.
At the time of his death, he had published over 60 articles and 4 books.
Founded in 1997, the company has published over 300 books.
He has published over 250 research papers and a dozen books.