Minecraft wiki entry for Armor_farming, associated text: 1 Villager Trading Method
1.1 Getting emeralds
1.1.1 Redstone farm & trade method
1.1.2 Raid farm method
1.2 Trading
2 Enchanting
2.1 Gathering enchanted books
2.1.1 Trade with Villagers
2.1.2 Books in enchanting table
2.1.3 Finding in loot
2.2 Gathering Armor, Anvils, and Levels
2.2.1 Armor
2.2.2 Anvil
2.2.3 Obtaining Levels
2.3 Combining Books
3 Zombie Armor Farm (Bedrock version)