@inbook {bjs15,
title = {Theories of proof-theoretic strength $\psi$($\Gamma_{\Omega+1}$)},
booktitle = {Concepts of Proof in Mathematics, Philosophy, and Computer Science},
series = {Ontos Mathematical Logic},
volume = {6},
year = {2016},
month = {January},
publisher = {De Gruyter},
organization = {De Gruyter},
isbn = {978-1-5015-0263-7},
url = {http://www.iam.unibe.ch/ltgpub/2015/bjs15.pdf},
author = {Ulrik Torben Buchholtz and Gerhard J{\"a}ger and Thomas Strahm},
editor = {Dieter Probst and Peter Schuster}
}