diff --git a/trimsp/src/TrimSPGUI/Chem.pm b/trimsp/src/TrimSPGUI/Chem.pm
index 8e869ca..f19b235 100644
--- a/trimsp/src/TrimSPGUI/Chem.pm
+++ b/trimsp/src/TrimSPGUI/Chem.pm
@@ -533,6 +533,7 @@ sub Elastof {
 }
 
 sub Stopicru {
+# Given the element it returns A-1 to A-5 of the ziegler tables
     my ($El) = @_;
     
     my %Stopicru = (
diff --git a/trimsp/src/TrimSPGUI4/Chem.pm b/trimsp/src/TrimSPGUI4/Chem.pm
index 8e869ca..f19b235 100644
--- a/trimsp/src/TrimSPGUI4/Chem.pm
+++ b/trimsp/src/TrimSPGUI4/Chem.pm
@@ -533,6 +533,7 @@ sub Elastof {
 }
 
 sub Stopicru {
+# Given the element it returns A-1 to A-5 of the ziegler tables
     my ($El) = @_;
     
     my %Stopicru = (
diff --git a/trimsp/src/trimsp7l.F b/trimsp/src/trimsp7l.F
index 946f4f9..f952b9a 100644
--- a/trimsp/src/trimsp7l.F
+++ b/trimsp/src/trimsp7l.F
@@ -489,23 +489,44 @@ C     part. refl. coeff. from Thomas et al.
       OPEN(UNIT=99,file=errnam,STATUS='new')
       OPEN(UNIT=11,file=innam,STATUS='unknown',ERR=13591)
 
+C     This part read the input file 
+
+C     Todo: Identify old format and read as follow, but also allow new
+C     format, possibly with more layers.
+C     First line: properties of projectile
       READ(11,*) Z1,M1,E0,Esig,ALPHA,ALPHASIG,EF,ESB,SHEATH,ERC
+C     Second line: simulation related parameters
       READ(11,*) NH,RI,RI2,RI3,X0,RD,CW,CA,KK0,KK0R,KDEE1,KDEE2,IPOT
      &     ,IPOTR,IRL
+C     Third line: layer structure. To be replaced by number of layers
+C     and then each layer with its properties: Thickness (DX), density
+C     (RHO), and correction factor (CK, it is always 1.0??)
       READ(11,*) DX(1),DX(2),DX(3),DX(4),DX(5),DX(6),DX(7),RHO(1),RHO(2)
      &     ,RHO(3),RHO(4),RHO(5),RHO(6),RHO(7), CK(1),CK(2),CK(3),CK(4)
      &     ,CK(5),CK(6),CK(7)
+C     Here we read the 7 layer structure
       DO I=1,7
+C     Atomic numbers
          READ(11,*) ZT(I,1),ZT(I,2),ZT(I,3),ZT(I,4),ZT(I,5)
+C     Mass numbers (amu)
          READ(11,*) MT(I,1),MT(I,2),MT(I,3),MT(I,4),MT(I,5)
+C     Concentration
          READ(11,*) CO(I,1),CO(I,2),CO(I,3),CO(I,4),CO(I,5)
+C     Surface binding energy
          READ(11,*) SBE(I,1),SBE(I,2),SBE(I,3),SBE(I,4),SBE(I,5)
+C     Displacement energy
          READ(11,*) ED(I,1),ED(I,2),ED(I,3),ED(I,4),ED(I,5)
+C     Bulk binding energy
          READ(11,*) BE(I,1),BE(I,2),BE(I,3),BE(I,4),BE(I,5)
+C     value A-1 of the ziegler tables
          READ(11,*) CH1(I,1),CH1(I,2),CH1(I,3),CH1(I,4),CH1(I,5)
+C     value A-2 of the ziegler tables
          READ(11,*) CH2(I,1),CH2(I,2),CH2(I,3),CH2(I,4),CH2(I,5)
+C     value A-3 of the ziegler tables
          READ(11,*) CH3(I,1),CH3(I,2),CH3(I,3),CH3(I,4),CH3(I,5)
+C     value A-4 of the ziegler tables
          READ(11,*) CH4(I,1),CH4(I,2),CH4(I,3),CH4(I,4),CH4(I,5)
+C     value A-5 of the ziegler tables
          READ(11,*) CH5(I,1),CH5(I,2),CH5(I,3),CH5(I,4),CH5(I,5)
       ENDDO