We generalise theorems of Khodorovskiy and Park-Park-Shin, and give new
topological proofs of those theorems, using embedded surfaces in the 4-ball and
branched double covers. These theorems exhibit smooth codimension-zero
embeddings of certain rational homology balls bounded by lens spaces.Comment: 27 pages, 25 figures. V2: Improved exposition incorporating referee's
suggestions. Accepted for publication in Q. J. Math. V3: minor correction
