Infinity, eternity, countlessness in Buddhism

I'm interested in concepts of infinity, eternity, countlessness, etc. in Buddhist thought. Could you please help me out with sources, both primary and secondary, where these concepts are used? I know that there are countless beings, that the world existed forever, that Buddha's knowledge is limitless, that there are countless Buddhas, countless universes. But it is extremely hard to pin down exact scriptures where these concepts are elaborated and to find secondary sources where the issues of infinity and eternity are discussed. Will be grateful for any help. Thanks!