sentences:  They are calculated for the Gaussian distribution of asperities
  
  For formula_120 the coefficients are
  
  The maximum relative error is formula_122.For formula_123 the coefficients are
  
  The maximum relative error is formula_125.The paper also contains the exact expressions for formula_118 
  
  where erfc(z) means the complementary error function and formula_128 is the modified Bessel function of the second kind.