What is >> Boswellia <<?

[Kelly McGrew]

The only reference I can find to Boswellia is in the Encyclopedia 
Britannica (15th ed., copyright 1987), vol. 4, page 940.  The article 
there indicates that Boswellia is the genus of trees from which 
frankincense is obtained.  The source is especially B. frereana, B. 
bhaw-dajiana, and B. carteri.  Incisions are made in the trunk of the 
tree and the frankincense is the juice which exudes from the tree, 
hardening upon exposure to air.

There may be other species with medicinal uses, but I've not found 
them.