*-- Author : S.Burke / J.V. Morris
      DOUBLE PRECISION FUNCTION FKCHPR(NPROB,NFREE,IERR)
**********************************************************************                                        
*                                                                    *                                        
*  Inverse chi-sq probability                                        *                                        
*                                                                    *                                        
* ERROR CONDITIONS;                                                  *                                        
*       IERR =   0  ; normal termination                             *                                        
*   ->  IERR = 101  ; invalid probability cut                        *                                        
*   ->  IERR = 104  ; invalid value of NPROB or NFREE                *                                        
*                                                                    *                                        
*   ->  Fatal error                                                  *                                        
*                                                                    *                                        
* The function returns -1 for error 4, 0 or 10**10 for error 1       *                                        
*                                                                    *                                        
**********************************************************************                                        
*KEEP,FKECODE.                                                                                                
*KEND.                                                                                                        
*KEEP,FKNPL.                                                                                                  
*                                                                                                             
* Per-track values can go in H1WORK; note that LTRUE and LFIRST must                                          
* be set at least per event.                                                                                  
*                                                                                                             
* This is about 36k words long; the remaining common blocks are                                               
* about 3.6k in total. Some of this could be in /H1WORK/, but the                                             
* blocks would have to be reorganised.                                                                        
*                                                                                                             
* /FKPROJ/                                                                                                    
* /FKFILT/                                                                                                    
* /FKSMTH/                                                                                                    
* /FKINT/                                                                                                     
* /FKRSID/                                                                                                    
* /FKTRUE/                                                                                                    
* /FKDBG/                                                                                                     
*KEEP,FKRJCT.                                                                                                 
*KEND.                                                                                                        
**********************************************************************                                        
**********************************************************************                                        
         CALL FKERR(IUTIL,IROUT,IFATAL,IINV,IERR)
     &   CALL FKERR(IUTIL,IROUT,IFATAL,IINF1,IERR)
*