Jan Hartman
Principia, Volume 13-14, 1995, pp. 257 - 268
Jan Hartman
Principia, Volume 21-22, 1998, pp. 327 - 335
Jan Hartman
Principia, Volume 29, 2001, pp. 198 - 200
Jan Hartman
Principia, Vol 59-60, 2014, pp. 83 - 100
https://doi.org/10.4467/20843887PI.14.004.2974