@article{JIS_2004__7_1_a6,
     author = {Schlage-Puchta, Jan-Christoph and Spilker, J\"urgen},
     title = {The greatest common divisor of two recursive functions},
     journal = {Journal of integer sequences},
     publisher = {mathdoc},
     volume = {7},
     number = {1},
     year = {2004},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2004__7_1_a6/}
}