World heritage site about Ha Long Bay: http://whc.unesco.org/pg.cfm?cid=31&id_site=672
Official website of Ha Long Bay: http://www.halong.com/
Photos of Ha Long Bay: http://www.terragalleria.com/vietnam/vietnam.halong.html
Lonelyplanet: http://www.lonelyplanet.com
Travelfish: http://www.travelfish.org
UK Climbing: http://www.ukclimbing.com
GREEN MANGO HOTEL- RESTAURANT in Hanoi and Cat Ba: http://www.greenmango.vn/
Cat Ba: http://www.catba.com.vn
Matt Maddaloni, deep water soloing Vietnam
SMART NEST TRAVEL
http://www.blognesthostels.com/vietnam/boat-trip-in-halong-bay-unforgettable/julia
TRIPADVISOR travel online
http://www.tripadvisor.com/ShowUserReviews-g737051-d386683-r22406252-Cat_Ba_Island-Cat_Ba.html
http://hanknmarla.net/blog/?cat=23
http://www.travelblog.org/Asia/Vietnam/Red-River-Delta/Cat-Ba-Island/blog-347995.html