Additional Spell Memorizatioin Items. Stackable?

Can items that add the ability to memorize additional spells be stacked? For example, could I wear an amulet that grants additional memorization of 1st, 2nd and 3rd spell slots and also gain additional 1st, 2nd and 3rd level spell slots from another item like a ring? On top of that could I use a third item like a sword that also grants more spell slots?

I know this will not work with armor class items. You can't wear two ring of protections for example and get twice the bonus. I just wanted to be sure before I commit pips toward Katana for Zerth Blade.