Amir M. Ben-Amram Omer Berkman Holger Petersen Element distinctness on one-tape Turing machines: a complete solution. 81-94 2003 40 Acta Inf. 2 http://dx.doi.org/10.1007/s00236-003-0125-8 db/journals/acta/acta40.html#Ben-AmramBP03