BibTeX: 
@article{Universal_Turing_MachineAFP,
author = {Jian Xu and Xingyuan Zhang and Christian Urban and Sebastiaan J. C. Joosten},
title = {Universal Turing Machine},
journal = {Archive of Formal Proofs},
month = feb,
year = 2019,
note = {\url{http://isaafp.org/entries/Universal_Turing_Machine.html},
Formal proof development},
ISSN = {2150914x},
}
