@article{PMIHES_1989__69__42_0,
     author = {Bourgain, Jean and Furstenberg, Harry and Katznelson, Yitzhak and Ornstein, Donald S.},
     title = {Appendix on return-time sequences},
     journal = {Publications Math\'ematiques de l'IH\'ES},
     pages = {42--45},
     publisher = {Institut des Hautes \'Etudes Scientifiques},
     volume = {69},
     year = {1989},
     language = {en},
     url = {http://www.numdam.org/item/PMIHES_1989__69__42_0/}
}