The inversion of nabla Laplace transform, corresponding to a causal sequence,
is considered. Two classical methods, i.e., residual calculation method and
partial fraction method are developed to perform the inverse nabla Laplace
transform. For the first method, two alternative formulae are proposed when
adopting the poles inside or outside of the contour, respectively. For the
second method, a table on the transform pairs of those popular functions is
carefully established. Besides illustrating the effectiveness of the developed
methods with two illustrative examples, the applicability are further discussed
in the fractional order case