Left panel: distributions of maser spots of the typical kinds of maser transitions in W51-North, including H₂O, NH₃ (9,6), and CH₃OH 4₂–4₁ ones. Right panel: distributions of maser spots for the NH₃ (7,7), (7,6), and (8,6) transitions in W51-North, overlaid on that of H₂O maser for comparison. The white contours in both panels show the 1.3 mm continuum emission detected from the ALMA archived data.