I'm doing a Diff in Diff and I'm first making a graph I put in the following command:
twoway (line students year if university==1) (line students year if university==2, xline(2011)), xlabel(2003(2)2014) legend(lab(1 "Erasmus") lab(2 "Tilburg") )

however I get the error
xlabel(2003(2)2014) is not a twoway plot type

then I tried putting in
twoway (line students year if university==1) (line students year if university==2, xline(2011)) legend(lab(1 "Erasmus") lab(2 "Tilburg") )

but then I get the error
option ) not allowed

how do I get past this error to get my plot?