@article{10_1017_S0017089512000158,
     author = {POWELL, GEOFFREY},
     title = {ON {THE} {DOUBLE} {TRANSFER} {AND} {THE} {f-INVARIANT}},
     journal = {Glasgow mathematical journal},
     pages = {547--577},
     year = {2012},
     volume = {54},
     number = {3},
     doi = {10.1017/S0017089512000158},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089512000158/}
}