Why is 3-D interaction so hard and what can we really do about it?

Julian E. Gómez Rick Carey Tony Fields Andries van Dam Dan Venolia Why is 3-D interaction so hard and what can we really do about it? 492-493 1994 conf/siggraph/1994 SIGGRAPH http://doi.acm.org/10.1145/192161.192299 db/conf/siggraph/siggraph1994.html#GomezCFDV94