Here are the links to the online textbook chapters:

Link to the Chapter 9: https://icomets.org/ush-textbook/ch9.pdf

Link to the Chapter 10: https://icomets.org/ush-textbook/ch10.pdf

Link to the Chapter 11: https://icomets.org/ush-textbook/ch11.pdf

Link to the Chapter 12: https://icomets.org/ush-textbook/ch12.pdf

Link to the Chapter 13: https://icomets.org/ush-textbook/ch13.pdf

Link to the Chapter 14: https://icomets.org/ush-textbook/ch14.pdf

Link to the Chapter 15: https://icomets.org/ush-textbook/ch15.pdf