survey of planetary nebulae in Andromeda (M31) – IV. Radial oxygen and argon abundance gradients of the thin and thicker disc. - Bhattacharya, Souradeep; Arnaboldi, Magda; Caldwell, Nelson; Gerhard, Ortwin; Kobayashi, Chiaki; Hartke, Johanna; Freeman, Kenneth C; McConnachie, Alan W; Guhathakurta, Puragra (Monthly Notices of the Royal Astronomical Society, 2022)