In complex analysis, a branch (also called a sheet) is a portion of the range of a multivalued
function over which the function is single-valued. Combining all the sheets gives
the full structure of the function. It is often convenient to choose a particular
branch of a function to work with, and this choice is often designated the "principal branch" (or "principal sheet").
Harary, F. Graph Theory. Reading, MA: Addison-Wesley, 1994.Lu, T. "The Enumeration
of Trees with and without Given Limbs." Disc. Math.154, 153-165,
1996.Schwenk, A. "Almost All Trees are Cospectral." In New
Directions in the Theory of Graphs (Ed. F. Harary). New York: Academic
Press, pp. 275-307, 1973.
in a tree is a maximal subtree
containing 
as an endpoint (Harary 1994, p. 35).
