Mishna Berura Page 284a: Chapter 422;2 to 422;4 The Davening on Rosh Chodesh - part 3 Rabbi AE Glatt
Shmiras Halashon - Shaar Hazechira 11-5 Rabbi MY Edelman
Kitzur Shulchan Aruch Chapter 128;15 - 129;2 The laws of the month of Elul - Rosh Hashana Rabbi D Brett
Chovos Halevavos - Gate 6 Humility Part 6 Chapter 4.2 Rabbi D Brett