Citations:dabba


 * 2008 Gokhale et al., Engineering Mathematics I, p. 10.2, Nirali Prakashan ISBN 8190693549.
 * 2013 Shackle, Expectation, Enterprise and Profit, p. 50, Routledge, 2013 ISBN 1136518134.
 * 1982 Williams, Geotechnics, Level IV, p. ix, Van Nostrand Reinhold 1982, ISBN 0442303505.