Thank you for your answer. But I'm not using an external survey page, because I can not directly link to a special survey page (no special ID in the URL). So my last solution is to propose an hyperlink at the bottom of certain pages
of "survey 1" (within a text format question), this URL links to another (anonymous) EFS survey ("survey 2").
But then in survey 2, when I click on "submit" button of the only page, it should go to a final page. BUT instead unipark displays "An internal application error has occured. The data transmitted by your browser is not valid and cannot be processed by the system. Please restart the survey.
". (survey 1's ID=236447 ; click on "QUITTER" in page n°1306575; ID os survey 2 is 237259).
I tried to change the URL of survey 2 as you said (http://ww3.unipark.de/uc/etude_regio...turn_tic=#tic#
) but this survey must have at least an URL parameter "a=" to return the lfdn (currently the survey 2's URL is "http://ww3.unipark.de/uc/toure_Unive...ier_1/061b/?a= ").
What should I do? Thank you !!!