Hi Maria,
You'll want to start at our catalog's advanced search page here:
http://unomaha.worldcat.org/advancedsearch
Next, in the "keyword" search box, you'll type in: opposing viewpoints + (your subject). So, if your subject is health care, you'd type: opposing viewpoints + health care. Then down where it says "format," limit to "book." Then hit the search button. It'll take you to a page that looks like this:
http://unomaha.worldcat.org/search?q=kw%3Aopposing+viewpoints+%2B+health+care&qt=advanced&dblist=638
I hope this helps. Please let me know if you have further questions. Have a great day!
Danielle S.