Looking for a historical text or a contemporary study of such text on how it is that this world is or isn't a "pure land"

Looking for a primary source (an actual historical text) or a secondary source (a formal study of a historical text or texts), on how it is that this world is or isn't a "pure land". Presumably the Buddha Sakyamuni has or had a pure land? I've read a lot of Buddhist scholarship, so please don't be shy in recommending anything at all, in English or translatable somehow.