On reference "Reference" is misguided, The word apple and the thing that is an apple are one and the same. They mean the same thing. They are not merely static neutral particles that form sentences or physical reality respectively. They have an active, synergistic role in the world, and discourse, which makes them meaningful. To talk of them as "mind independent" is nonsense, as it introduces a bifurcation of worlds as the foundation for its sensibility, but the mind hardly ends, or is encompassed by the skull. The word "apple" a drawing of an "apple" or a tasty apple can all be used to convey the same meaning, , as well as being used to convey different meanings, depending on how they're used. The most abstract of concepts are no less deprived of physical counter parts than apples are, in the way of words spoken, gestures made, or written forms. Things are not either in the mind, or external to the mind, it is always both and neither.
Lastly, a thing that is independent of the mind, in the sense of not participating in discourse, or life has no significance in any sense, and by this very stipulation cannot possibly exist.