specified by the user. In the latter case, \code{BIRTH} and/or
\code{DEATH} may be used of the primitives of \code{birth} and
\code{death} are known. In these functions time is the formal argument
specified by the user. In the latter case, \code{BIRTH} and/or
\code{DEATH} may be used of the primitives of \code{birth} and
\code{death} are known. In these functions time is the formal argument