ABSTRACT
The index i may be thought to represent anyone element of the column matrix or it may, depending on the context of the discussion, represent the entire matrix as implied by Eq. (1.2). Such an index is called a free index since it is "free" to take on three values in three-dimensional space: namely, x, y, and z. In this book any English (i.e., Latin) letter with the exception of the letters x, y, and z may be used as a free index in place of i above for three-dimensional spaces. Furthermore, any Greek letter with the exception of JL and v may be used as a free index above for two-dimensional spaces.
