Sentence:  The element "a" can be uniquely represented in the form "r" + "t", where ["rt"] = 0, "t" is nilpotent and "r" is a <WSD>quasiregular</WSD> element of "G" ([1]; p. 108). 
Meaning of the word marked with <WSD> tags:  Such that 1 − r is a unit (has a multiplicative inverse).