I could be wrong, but are you sure you aren't over complicating this. Your post said you need to write an "essay", yet the question sounds like you are doing a research paper. If I'm wrong 'ignore me' (which I know I needed tell you).
If you just want an existing research paper or article to quote this is what I did (it's amazing what you can find 'surfing the net'):
I typed 'nursing research journals' on goggle and hit return.
That brought up a variety of options from which I randomly chose the following:
A hotlink labeled 'NURSING JOURNAL RESEARCH (perpendicular line I can't make on my keyboard) HighBeam.com
The above mentioned hotlink has the web address www.highbeam.com/NursingJournals
listed just below it.
This took me to Highbeam research webpage (the addr. line on my computer when at the Highbeam research webpage reads very similar to the addr. above; there is a little more info. attached--(aka, use the hotlink not the web address to get there).
From the highbeam research webpage, where it says 'search the archives' I entered the keyword phrase 'risk assessment tools for pressure sores' and hit the 'search the archives' button.
I immediately went to a listing of 74 matching articles; I believe they contain the kind of information you are looking for.
When I was on the page that listed 74 matching articles my addr. line read http://www.highbeam.com/Search?searc...pressure+sores
I believe you can copy and paste the above address and ignore all the other stuff.
Please forgive me for over elaborating; I felt sharing the process of finding it might help down the road, as opposed to just giving you the website.
I have no idea what access to 'Highbeam research' full length articles cost, however; there's a 7 day free trial. We all know how that goes -- they are hoping you don't bother to cancel. Anyway if you get the journal names, or book names or whatever off of highbeam you might be able to access the articles somewhere else like the library, or ask your school librarian for help.
Again, if you just need to write an essay that gets you in the mode of thinking 'evidence based nursing' try this:
search '146 years ago' from allnurses.com website. Somebody previously posted an article about Ignez Semmelweis (not sure of spelling). It was a great article and it bespeaks towards the end of the article about the dangers of ignoring EBN. This guy provided EBN data that could have prevented puerperal fever in large part; he did so at a time prior to the use of EBN and offended his colleagues. Read the article. My thanks to whoever posted it to begin with.
p.s. On my selfish part I am starting to develop a portfolio of "technical writing" examples. It took me 10 minutes to do the search and about an hour and a half to write this reply. I tried running through the instructions myself, from scratch, after writing this. It worked for me. Let me know if you found this easy to follow, or terribly convoluted (either way, I'd really like honest feedback).