Plane & spherical trigonometry : a tetrahedron approach 
Mamhot, Millard R. 
 -  Unlimited Books Library Services & Publishing Inc.,  2015 
 - vi, 213 p. 
978-9-71965405-6
Trigonometry.
F 516.24 P7121 2015
                        978-9-71965405-6
Trigonometry.
F 516.24 P7121 2015