“…The obstacle problem has been studied for bounded sets in (weighted) R n (see, e.g., Heinonen-Kilpeläinen-Martio [20] and the references therein), and later also for bounded sets in more general metric spaces (see, e.g., Björn-Björn [3], [4], [5], Björn-Björn-Mäkäläinen-Parviainen [6], Björn-Björn-Shanmugalingam [8], Kinnunen-Martio [25], Kinnunen-Shanmugalingam [26], and Shanmugalingam [31]). The double obstacle problem has also been studied (see, e.g., Farnana [13,14,15,16] and Eleuteri-Farnana-Kansanen-Korte [12]).…”