Anyone who requires a visa to enter Germany must visit the page of your local German embassy or consulate for updated information on visa applications. An invitation letter for a visa application for participating in the conference will be provided upon request.
Further information about German travel rules and regulations (incl. visa applications) can be found on the official pages at this link:
German Foreign Office (Auswaertiges Amt)
An important advice:
We strongly recommend to apply for your visa well in time, as the present political situation in Europe may cause longer periods for processing and approval at the German embassies.