Less compiler css

WriteFreely
1 
less>lessc app.less --clean-css="--s1 --advanced" $(CSSDIR)write.css
ParseError: Unrecognized input. Possibly missing '(' in mixin call. in G:\less\core.less on 
line 78, column 19:
77                      h2#title {
78                              .article-title;
79                      }

less compiler problem on windows .
Does anyone have an idea?

lessc app.less --clean-css="--s1 --advanced" $(CSSDIR)write.css
2

I tryied many times
and finally I used some online tools , but for app.less I needed multi less convert to one file.

and I removed less version 4 and installed 3.5.3
npm install -g less@3.5.3

Its worked