@article{doi:10.1302/0301-620X.62B4.7430217,
author = {Hardcastle, PH and Ross, R and Hamalainen, M and Mata, A},
title = {Catterall grouping of Perthes' disease. An assessment of observer error and prognosis using the Catterall classification},
journal = {The Journal of Bone & Joint Surgery British Volume},
volume = {62-B},
number = {4},
pages = {428-431},
year = {1980},
doi = {10.1302/0301-620X.62B4.7430217},
url = {https://doi.org/10.1302/0301-620X.62B4.7430217}
}