Update my answer to Exercise 4.6.

Modified is the following file:

	Exercise_4.6.scm

Thank you!
							Lawrence X. Amlord
							  Feb 15th, 2014
							  Fuzhou, China
Add my answer to Exercise 4.22.

Included is the following file:

	Exercise_4.22.scm

Thank you!
							Lawrence X. Amlord
							  Feb 15th, 2014
							  Fuzhou, China
Add my answer to Exercise 4.23.

Include is the following file:

	Exercise_4.23.tm

Thank you!
							Lawrence X. Amlord
							  Feb 16th, 2014
							  Fuzhou, China
Update my answer to Exercise 4.23.

The following file has been modified:

	Exercise_4.23.tm

Besides, I've add in the PDF it generated:

	Exercise_4.23.pdf

Thank you!
							Lawrence X. Amlord
							  Feb 17th, 2014
							  Fuzhou, China