D’heer, E., B. Vandersmissen, W. De Neve, P. Verdegem, and R. Van de Walle. “What Are We Missing? An Empirical Exploration in the Structural Biases of Hashtag-Based Sampling on Twitter”. First Monday, Vol. 22, no. 2, Jan. 2017, doi:10.5210/fm.v22i2.6353.