="citation web"><a rel="nofollow" class="external text" href="http://www.zamperla.com/en/product/157/surf-s-up.html">"Zamperla – Surf's Up"</a>. Zamperla<span class="reference-accessdate">. Retrieved 19 May 2011</span>.</span><span title="ctx_ver=Z39.88-2004&amp;rfr_id=info%3Asid%2Fen.wikipedia.org%3ADisk%27O&amp;rft.btitle=Zamperla+%E2%80%93+Surf%27s+Up&amp;rft.genre=book&amp;rft_id=http%3A%2F%2Fwww.zamperla.com%2Fen%2Fproduct%2F157%2Fsurf-s-up.html&amp;rft.pub=Zamperla&amp;rft_val_fmt=info%3Aofi%2Ffmt%3