Movies, music and books require investments of money and time.

Talking books require the use of a specialized playback device.

The latter book required 9 years of research to recover many songs that were never written to paper.

The book took over 24 hours to bind and required a special press to bind all the pages together.

The book requires only a source of light.

A book, on the other hand, generally requires more intellectual application from its readers but is good for delivering detailed information.

A book this long and full requires a mammoth amount of fact checking.

In practice this book requires a finer-grained view than that of Figure 1.1.

The world has changed and people do not have the time to give that a book requires.

The book requires no great musical literacy of the reader.