Geo-Wiki.Org: The Use of Crowdsourcing to Improve Global Land Cover. - Steffen Fritz; Ian McCallum; Christian Schill; Christoph Perger; Roland Grillmayer; Frédéric Achard; Florian Kraxner; Michael Obersteiner (Remote. Sens., 2009)

Building a Crowd-Sourcing Tool for the Validation of Urban Extent and Gridded Population. - Steffen Fritz; Linda M. See; Ian McCallum; Christian Schill; Christoph Perger; Michael Obersteiner (ICCSA (2), 2011)

Geo-Wiki: An online platform for improving global land cover. - Steffen Fritz; Ian McCallum; Christian Schill; Christoph Perger; Linda See; Dmitry Schepaschenko; Marijn Van der Velde; Florian Kraxner; Michael Obersteiner (Environ. Model. Softw., 2012)

Assessing the Accuracy of Volunteered Geographic Information arising from Multiple Contributors to an Internet Based Collaborative Project. - Giles M. Foody; Linda M. See; Steffen Fritz; Marijn Van der Velde; Christoph Perger; Christian Schill; Doreen S. Boyd (Trans. GIS, 2013)

A Meta-Analysis on the Return on Investment of Geospatial Data and Systems: A Multi-Country Perspective. - Natalie Trapp; Uwe A. Schneider; Ian McCallum; Steffen Fritz; Christian Schill; Maria Teresa Borzacchiello; Christine Heumesser; Max Craglia (Trans. GIS, 2015)

Increasing the Accuracy of Crowdsourced Information on Land Cover via a Voting Procedure Weighted by Information Inferred from the Contributed Data. - Giles M. Foody; Linda See; Steffen Fritz; Inian Moorthy; Christoph Perger; Christian Schill; Doreen S. Boyd (ISPRS Int. J. Geo Inf., 2018)