@article {bonito2020finite, title = {Finite element approximation of an obstacle problem for a class of integro{\textendash}differential operators}, journal = {ESAIM: Mathematical Modelling and Numerical Analysis}, volume = {54}, number = {1}, year = {2020}, pages = {229{\textendash}253}, publisher = {EDP Sciences}, author = {Bonito, Andrea and Wenyu Lei and Salgado, Abner J} }