Kalguuran Text

Can someone explain in details where can I find Kalguuran Text please? I have quest in act 3 and I'm in act 8 right now. Does it means that this text can be found only in act 3 or I can get it in any other act? Is it located in specific location or is it random drop? please help me. :)

This is specific to the new Expedition content so keep in mind there is no immediate reward of gear or skill points. I've found them inside of the rare 'logbook' drops from league content - and inside those only in the secret/hidden underground passages. You turn them into Dannig for lore unlocks. Maybe after enough you get something more tangible but don't worry too much about them for now.