1
by Visvizi, Anna
Published 2020
MDPI - Multidisciplinary Digital Publishing Institute

2
by Lytras, Miltiadis
Published 2019
MDPI - Multidisciplinary Digital Publishing Institute

3
by Rittmann, Günter
Published 2014
Nomos Verlagsgesellschaft mbH & Co. KG

4
by Heßler, Martina
Published 2020
Nomos Verlagsgesellschaft mbH & Co. KG