Viking is a company that bought the plans for the twotter from Dehaviland. They are currently about to roll the first production -400 twotters off the line. Viking Air. I do believe that they own the beaver, otter and caribou as well. Not sure about the buffalo though. I would think that for any needs of manuals etc... they would be the company to contact. Hope this helps. Also I do believe that Viking is thinking aobut trying a limited run of producing the other aircraft.