Is that the onlt size you have? There really isn't any chance of clearing things up with such a tiny image. Where did the image come from? Did you scan it, photograph it, or did it come as a digital file?
I cme up with 2 versions: One via Auto-Tone and Image>Contrast, the other with Filter>Smart Sharpen. The second one, even with fading the Smart Sharpen, has artifacts. I don't know how imprortant that is to you.