I have a set of figures that I would like to show as grid for a publication. I currently just export the figure as an eps and use another software package to add Labels (A,B,C,D) to each panel of the figure. This is rather tedious to do. Is there a way to label each panel in Mathematica? For example is it possible to label each panel of the following grid?
a = Plot[Sin[x], {x, -Pi, Pi}];
b = Plot[Cos[x], {x, -Pi, Pi}];
c = Plot[ArcSin[x], {x, -Pi, Pi}];
d = Plot[ArcCos[x], {x, -Pi, Pi}];
Grid[{{a, b}, {c, d}}, Spacings -> {1, 2}, Frame -> All]