  : I Listed this, as it looked like the single sentences for structures and advantages/disadvantages could probably be expanded, and explained, rather than that there are particular grammatical or other errors in the text.  I don't know of more material that belongs here, but it seemed likely, when I looked at it, that there was some, but I don't know enough about the subject to add anything, so added it to cleanup, so if there was anything useful to add, someone who knows about the subject can add it.  