@article{10_4171_ggd_71,
     author = {Adrian Ioana and Alexander S. Kechris and Todor Tsankov},
     title = {Subequivalence relations and positive-definite functions},
     journal = {Groups, geometry, and dynamics},
     pages = {579--625},
     year = {2009},
     volume = {3},
     number = {4},
     doi = {10.4171/ggd/71},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/ggd/71/}
}