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Clerkin, James (2004), 2MASS study of candidate precursors to UCHII regions (PDF), Universidade do Porto, retrieved 30 September 2017 http://eoin.clerkin.biz/papers/2MASS-study-of-candidate-precursors-to-UCHII-regions.pdf
Clerkin, James (2004), 2MASS study of candidate precursors to UCHII regions (PDF), Universidade do Porto, retrieved 30 September 2017 http://eoin.clerkin.biz/papers/2MASS-study-of-candidate-precursors-to-UCHII-regions.pdf