Ballone, F. A. "On Volterra Spaces." Masters thesis, Youngstown State University, Jun. 2010.Beanland, K.; Roberts, J. W.; and Stevenson, C. "Modifications of Thomae's Function and Differentiability." Amer. Math. Monthly116, 531-535, 2009.Bruckner, A; Bruckner, J.; and Thomson, B. Elementary Real Analysis, 2nd ed.. Upper Saddle River, NJ: Prentice Hall, 2008.Dixon, R. Mathographics. New York: Dover, pp. 177 and 184-186, 1991.Tall, D. "The Gradient of a Graph." Math. Teaching111, 48-52, 1985.Trott, M. The Mathematica GuideBook for Programming. New York: Springer-Verlag, pp. 32-33, 2004. http://www.mathematicaguidebooks.org/.
和 
為實數 (通常取 
和 
)。狄利克雷函式定義為
處連續，在有理數 
處不連續 (雖然無理點 
周圍的小區間包含無限多個有理點，但這些有理數將具有非常大的分母)。當從沿著直線 
的角落以正常視角觀察時，象限的歐幾里得果園會變成修改後的狄利克雷函式 (Gosper)。