@article{10_4064_fm_89_1_5_11,
     author = {Hans Carstens},
     title = {Reducing hyperarithmetic sequences},
     journal = {Fundamenta Mathematicae},
     pages = {5--11},
     publisher = {mathdoc},
     volume = {89},
     number = {1},
     year = {1975},
     doi = {10.4064/fm-89-1-5-11},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-89-1-5-11/}
}