  We revisit the linearization theorems for proper Lie groupoids around general
orbits (statements and proofs). In the the fixed point case (known as Zung's
theorem) we give a shorter and more geometric proof, based on a Moser
deformation argument. The passing to general orbits (Weinstein) is given a more
conceptual interpretation: as a manifestation of Morita invariance. We also
clarify the precise conditions needed for the theorem to hold (which often have
been misstated in the literature).
