In the _New Grove Dictionary_ will be found an extensive article "Pianoforte," and a shorter note, "Square pianoforte," with a reference back to the larger article; which has (as usual) an excellent bibliography. I don't know that "Grove" is available online - but Hey, take a nostalgic trip back in time, to that quaint world of print and paper, those long-ago days of yesteryear. There is a certain sensory satisfaction to the look and feel of an actual _book_; the weight, and heft, the texture, the aroma. Many have forgotten the skills needed to operate one, but much of it is intuitive.