Phys 276 Class Notes, Sept 24
 1.   Chi-squared minimization and linear fitting
   see Taylor, Chapter 8 (pp 181-190)
   or Lyons, Sect. 2.3-2.4 (pp 49-56)
2.    Magnet Fields from a current source
   see Resnick, Halliday and Krane, Chapter 35