At least one book has been written on the subject.

A book could be written on the subject of your question.

He is not known to have written any books on the subject.

Later in life he wrote on the subject through many of his books.

He has written a number of books on the subject.

I have not yet seen anything in writing on the subject.

It's the reason little has been written on the subject.

He wrote a book on the subject, which was published in 1836.

He is also known to write on the subject of politics.

Indeed there has been quite a lot written on the subject.