Here is the series naming:
Ms. Barbara's Exploration of Female Supremacy 1 - Make Him Work For It - Victoria West
Ms. Barbara's Exploration of Female Supremacy 2 - The Interrogation - Victoria West
Ms. Barbara's Exploration of Female Supremacy 3 - Leather Slave - Victoria West
Ms. Barbara's Exploration of Female Supremacy 4 - Chastity Games - Victoria West
Ms. Barbara's Exploration of Female Supremacy 5 - Training Kevin - Victoria West
And seems like the fourth book is missing. So here it is: