@article{10_4064_aa_52_2_141_145,
     author = {Ekkehard Kr\"atzel},
     title = {The distribution of powerful integers of type 4},
     journal = {Acta Arithmetica},
     pages = {141--145},
     publisher = {mathdoc},
     volume = {52},
     number = {2},
     year = {1989},
     doi = {10.4064/aa-52-2-141-145},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa-52-2-141-145/}
}