Some of those I know for sure come from FL. This includes the 2 amulets. I am not sure about Unholy Resistsance, but it might come from FL too. The last time I checked, Jute's site was not updated for spellbooks and amulets introduced in C5.
Edit: If you do a search on this website forum, you can probably find the names of the mobs in FL which drop the spellbooks. And don't use a physical skill (suach as Hammer Crush) on Antelopes or Buffalo unless you're in a group, because they will morph into a whole bunch of mobs.
SB Greater might Frost Iron Golem
SB Greater shield Frost Buffalo
SB Unholy resistance Ursus
SB Erase Elder Lost Watcher
SB Mana burn Lost Gargoyle Youngling
AM Earth chant Frost Buffalo
AM War chant Frost Buffalo
all this mobs are allocated in Frozen Labyrinth. and like Oldfart say careful with those mobs he said unless your an AoE class they give a good xp but they pack quite a punch. :p