2011 · Friederike Wittig, Marianne Eisinger-Watzl, et al. · Organic Eprints (International Centre for Research in Organic Food Systems, and Research Institute of Organic Agriculture) · 1
2015 · Wittig, Friederike Anna, Justus Liebig University Giessen · University writing server of the Justus Liebig University Giessen (Justus-Liebig-Universität Gießen)