@article{10_37236_8579,
     author = {Bernhard Gittenberger and Isabella Larcher},
     title = {Distribution of variables in lambda-terms with restrictions on {De} {Bruijn} indices and {De} {Bruijn} levels},
     journal = {The electronic journal of combinatorics},
     year = {2019},
     volume = {26},
     number = {4},
     doi = {10.37236/8579},
     zbl = {1431.05014},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/8579/}
}