Webb-Robertson BJM, HK Wiberg, MM Matzke, JN Brown, J Wang, JE McDermott, RD Smith, KD Rodland, TO Metz, JG Pounds, and KM Waters.  2015.  "Review, Evaluation, and Discussion of the Challenges of Missing Value Imputation for Mass Spectrometry-Based Label-Free Global Proteomics."  Journal of Proteome Research 14(5):1993-2001.  doi:10.1021/pr501138h