SUBROUTINE KNVTX3(NTRK, ITRK, X)
 
C  >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
C  Returns intersection point in 3-d of several tracks, assuming that
C  the tracks are straight lines. This routine is used to obtain an initial
C  guess for the vertex in a full vertex fit. No errors are returned.
C
C  NTRK    integer variable (read)
C          Number of tracks
C
C  ITRK    integer array (read)
C          List of tracks in KN list to use
C
C *X       real array (write)
C          (x,y,z) intersection point. If it cannot be determined, it is
C          set to (0,0,0).
C  >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>