Hi everyone, I've set some method "[", "|", "&", etc.. to work with specific S4 object. So now, I'm trying to comment this functions in a Rd file. Usual functions are describe as : \S4method{length}{motiv}(x) where "motiv" is my S4 object taking an argument x. Unfortunatly, \S4method{[}{motiv}(x) generates an error when using the check function : Bad \usage lines found in documentation object 'motiv-methods': <unescaped bksl>S4method{]}{motiv}(x) Functions with \usage entries need to have the appropriate \alias entries, and all their arguments documented. The \usage entries must correspond to syntactically valid R code. See the chapter 'Writing R documentation files' in manual 'Writing R The "[" character seems to be not allowed in the description of the S4method. \[ does not change anything. Is there a way to use special character ([, &, |, ...) in the description of S4method ? Thanks. Arnaud Droit.