@article{BMMS_2010_33_3_a7,
     author = {Charinthip Hengkrawit and Vichian Laohakosol and Patanee Udomkavanich},
     title = {Rational {Recursive} {Equations} {Characterizing} {Cotangent-tangent} and {Hyperbolic} {Cotangent-tangent} {Functions}},
     journal = {Bulletin of the Malaysian Mathematical Society},
     year = {2010},
     volume = {33},
     number = {3},
     url = {http://geodesic.mathdoc.fr/item/BMMS_2010_33_3_a7/}
}