^ Gradshteyn and Ryzhik 3.155.7 and 3.169.9, taking due account of the difference in notation from Abramowitz and Stegun.

Lew et al., 'On the Average Distances in a Circular Disc' (1977). Rota, Gian-Carlo (1997), Introduction to Geometric Probability, Lezioni Lincee, Cambridge University Press, pp. 46–50.

^ In higher dimensions, the Euler characteristic of a closed ball remains equal to +1, but the Euler characteristic of an open ball is +1 for even-dimensional balls and −1 for odd-dimensional balls.

(1989), Combinatorial Group Theory: A Topological Approach, London Mathematical Society Student Texts, vol. 14, Cambridge University Press, p. 79, ISBN 9780521349369.

^ Maudlin, Tim (2014), New Foundations for Physical Geometry: The Theory of Linear Structures, Oxford University Press, p. 339, ISBN 9780191004551.

(2013), Journey into Mathematics: An Introduction to Proofs, Dover Books on Mathematics, Courier Dover Publications, p. 44, ISBN 9780486151687. (2013), Intuitive Concepts in Elementary Topology, Dover Books on Mathematics, Courier Dover Publications, p. 58, ISBN 9780486275765. ^ a b Clapham, Christopher Nicholson, James (2014), The Concise Oxford Dictionary of Mathematics, Oxford University Press, p. 138, ISBN 9780199679591.

A disk is said to be closed if it contains the circle that constitutes its boundary, and open if it does not. In geometry, a disk (also spelled disc) is the region in a plane bounded by a circle.

Disk geometry calculator