Sierra, Tracy (3) Tracy, Brian (3) Deonn, Tracy (3) Helmold, Marc (iu International University Of Applied Sciences, Kucuk Yilmaz, Ayse (eskisehir Technical University, Dathe, Tracy (macromedia University Of Applied Sciences, Martensen, Malte ( Iu International University Of Applied Sciences (1) Vonder Brink, Tracy (1)