We give a short proof of the Marker–Steinhorn theorem for o-minimal expansions of ordered groups. The key tool is Ramakrishnan’s classification of definable linear orders in such structures.
"The Marker–Steinhorn Theorem via Definable Linear Orders." Notre Dame J. Formal Logic 60 (4) 701 - 706, November 2019. https://doi.org/10.1215/00294527-2019-0026