A good textbook on fuel cells in general is Fuel Cell Systems Explained by
James Larminie and Andrew Dicks (John Wiley & Sons, Chichester, UK, 2000).
It deals with many kinds of these devices and devotes one chapter exclusive
ly to membrane (PEM) fuel cells. The book covers, besides the cells themsel
ves, related equipment like dc-to-ac inverters.
The companies mentioned in the article all have Web sites.