[AdmSmith]

The article is not correct, a positron is not really antimatter, it is just an antiparticle. You need an antiproton as well, and then, with luck, you would have an antihydrogen atom.

This seems to have been http://en.wikipedia.org/wiki/Electron-positron_annihilation

[El Gato]

The article is not correct, a positron is not really antimatter, it is just an antiparticle.

It IS antimattter. Not an anti-atom, but electrons and positrons (anti-electrons) are matter. So are quarks and anti-quarks, although at that level the difference between matter and energy is somewhat fuzzy.