@article{10_4171_dm_x32,
     author = {Ben Heuer},
     title = {Cusps and $q$-expansion principles for modular curves at infinite level},
     journal = {Documenta mathematica},
     pages = {2385--2439},
     year = {2022},
     volume = {27},
     doi = {10.4171/dm/x32},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/dm/x32/}
}