diff --git a/tracy/tracy/inc/tracy_global.h b/tracy/tracy/inc/tracy_global.h
index 53b5ff5a916a79e55dd80d9dc1d21f0b71a16758..b45859a3fe8a6ec098842eb0f58b379fa597e8f8 100644
--- a/tracy/tracy/inc/tracy_global.h
+++ b/tracy/tracy/inc/tracy_global.h
@@ -81,18 +81,18 @@ struct MpoleType {
   // Displacement Errors
   Vector2     PdSsys;    // systematic [m] 
   Vector2     PdSrms;    // rms [m]
-  Vector2     PdSrnd;    // random number
+  Vector2     PdSrnd;    // random error? [m]
   // Roll angle
   double      PdTpar;    // design [deg], if not equal zero, then skew multipole
   double      PdTsys;    // systematic [deg]
   double      PdTrms;    // rms [deg]
-  double      PdTrnd;    // random number
+  double      PdTrnd;    // random error??? [deg]
   // Multipole strengths
   mpolArray   PBpar;     // design
-  mpolArray   PBsys;     // systematic, with multipole errors
-  mpolArray   PBrms;     // rms
-  mpolArray   PBrnd;     // random number, random error?
-  mpolArray   PB;        // total
+  mpolArray   PBsys;     // systematic multipole errors
+  mpolArray   PBrms;     // rms multipole field errors
+  mpolArray   PBrnd;     // random number, random error?????
+  mpolArray   PB;        // total field strength
   int         Porder;    // The highest order in PB
   int         n_design;  // multipole order (design)
   pthicktype  Pthick;
diff --git a/tracy/tracy/src/t2elem.cc b/tracy/tracy/src/t2elem.cc
index 5cec54848b1ab18ed50cb304b5e26106712d75d7..a71654df21b1c51a57d182d8cef989d79a0df674 100644
--- a/tracy/tracy/src/t2elem.cc
+++ b/tracy/tracy/src/t2elem.cc
@@ -2756,7 +2756,34 @@ void Elem_Print(FILE *f, int Fnum1)
 
 double Mpole_GetPB(int Fnum1, int Knum1, int Order);
 
+/****************************************************************************
+ * double Elem_GetKval(int Fnum1, int Knum1, int Order)
+
+   Purpose: 
+       Get the n-th order integrated field strength of the element with
+       family index "Fnum1" and kid number "Knum1".
+
+   Input:
+       Fnum1:   Family number
+       Knum1:   kid number
+       Order:   field order
+        
+   Output:
+       none
+
+   Return:
+       Integrated n-th field strength
+
+   Global variables:
+       none
+
+   Specific functions:
+       none
+
+   Comments:
+       comments by Jianfeng Zhang  11/2010
 
+****************************************************************************/
 double Elem_GetKval(int Fnum1, int Knum1, int Order)
 {
   double    Result = 0.0;
@@ -3571,13 +3598,37 @@ void Mpole_SetPB(int Fnum1, int Knum1, int Order)
   cellconcat = false;
 }
 
+/**************************************************************************************
+double Mpole_GetPB(int Fnum1, int Knum1, int Order)
 
+  Purpose:
+         Return multipole strength (of order Order) for Knum1 element of
+      family Fnum1
+       Order =  2 for normal quadrupole, bn components
+             = -2 for skew quadrupole    an components
+       
+  Input:
+      Fnum1        family name
+      Knum1        kid number
+      Order        order of the multipole
+      
+  Output: 
+      None
+  
+  Return:
+      None
+     
+  Gloval variables:
+      None
+      
+  Specific functions:
+  
+  Comments:
+     None
+  
+**************************************************************************************/
 double Mpole_GetPB(int Fnum1, int Knum1, int Order)
 {
-  /*  Return multipole strength (of order Order) for Knum1 element of
-      family Fnum1
-       Order =  2 for normal quadrupole
-             = -2 for skew quadrupole                                        */
        
   MpoleType *M; /* Pointer on the multipole */