  An attempt is made to remedy confusing treatments of some basic relativistic
concepts and results in recent papers by Franklin (2010 {\it Eur. J. Phys.}
{\bf 31} 291-8) and by McGlynn and van Kampen (2008 {\it Eur. J. Phys.} {\bf
29} N63-N67). The authors' misconceptions are recurrent points in the
literature.
