It is mandatory for at least one author of an accepted paper to register and pay the conference fee in order for the paper to include the Conference Program.
If coauthor also like to register himself then each coauthor has to pay the 75 euro in order to get all things as covered in the fee. Students (include PhD students) may receive 50% support.
There is a possibility to decrease the conference fee up to 50%. Please send a mail to Ivan Ivanov email@example.com