Mishna Berura Page 288b: Chapter 428;2 to 428;4 How Does the Jewish Calendar Work? Rabbi AE Glatt
Shmiras Halashon - Shaar Hazechira 15-3 Rabbi MY Edelman
Kitzur Shulchan Aruch Chapter 131;2 - 131;4 The laws of Erev Yom Kippur Rabbi D Brett
Chovos Halevavos - Gate 6 Humility Chapter 6.3 Rabbi D Brett