(EN) Henry Gray, The Veins of the Upper Extremity and Thorax, in Anatomy of the Human Body, p. 664. URL consultato il 19 gennaio 2013.
«In obstruction of the superior vena cava, the azygos and hemiazygos veins are one of the principal means by which the venous circulation is carried on, connecting as they do the superior and inferior venæ cavæ, and communicating with the common iliac veins by the ascending lumbar veins and with many of the tributaries of the inferior vena cava.»
