We classify connected sums of three-dimensional lens spaces which smoothly bound rational homology balls. We use this result to determine the order of each lens space in the group of rational homology 3–spheres up to rational homology cobordisms, and to determine the concordance order of each 2–bridge knot.
"Sums of lens spaces bounding rational balls." Algebr. Geom. Topol. 7 (4) 2141 - 2164, 2007. https://doi.org/10.2140/agt.2007.7.2141