@article{article1b5513cd,
title   = {Free symmetric and unitary pairs in division rings with involution},
author = {Ferreira, Vitor de Oliveira and Gonçalves, Jairo Zacarias and Mandel, Arnaldo},
year = {2005},
doi = {10.1142/S0218196705002177},
journal   = {International Journal of Algebra and Computation}
}