References for the geometry of surfaces:
<ul>
 <li> Do Carmo
  <i> Differential Geometry of Curves and Surfaces</i>
   Prentice Hall 1976
 <li> O'Neill <i> Elementary Differential Geometry</i> Acad. Press 1997
<li> Spivak
  <i>A comprehensive introduction to Differential Geometry vol II </i>
  Publish & Perish 1999
 <li> Boothby
  <i> An introduction to differentiable manifolds and Riemannian geometry</i>
  Acad. Press 2002
<li> Hormander <i>Riemannian Geometry</i> Lund University 1990
<li> Pressley <i>Elementary Differential Geometry</i> Springer 2002
</ul>