diff --git a/README.md b/README.md
index 944963819332272c08db5a77685e10a03d274613..1a9c39aeceb7a63cabb054a9628fa18b6129c4f0 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # Concatenate
 
-_Concatenate_ is a command line program written in [Java](https://docs.oracle.com/javase/8/docs/technotes/guides/language/index.html) that allows building a supermatrix of characters from a set of multiple sequence alignments (MSA).
+_Concatenate_ is a command line program written in [Java](https://docs.oracle.com/javase/8/docs/technotes/guides/language/index.html) to build a supermatrix of characters from a set of multiple sequence alignments (MSA) in FASTA or PHYLIP format.
 
 ## Compilation and execution
 
@@ -8,6 +8,10 @@ The source code of _Concatenate_ is inside the _src_ directory and could be comp
 
 #### Building an executable jar file
 
+Clone this repository with the following command line:
+```bash
+git clone https://gitlab.pasteur.fr/GIPhy/Concatenate.git
+```
 On computers with [Oracle JDK](http://www.oracle.com/technetwork/java/javase/downloads/index.html) (6 or higher) installed, a Java executable jar file could be created. In a command-line window, go to the _src_ directory and type:
 ```bash
 javac Concatenate.java 
@@ -15,37 +19,51 @@ echo Main-Class: Concatenate > MANIFEST.MF
 jar -cmvf MANIFEST.MF Concatenate.jar Concatenate.class 
 rm MANIFEST.MF Concatenate.class 
 ```
-This will create the executable jar file `Concatenate.jar` that could be launched with the following command line model:
+This will create the executable jar file `Concatenate.jar` that could be run with the following command line model:
 ```bash
 java -jar Concatenate.jar [options]
 ```
 
 #### Building a native code binary
 
-On computers with the [GNU compiler GCJ](https://gcc.gnu.org/onlinedocs/gcc-4.2.4/gcj/) installed, a binary could also be built. In a command-line window, go to the _src_ directory, and type:
+Clone this repository with the following command line:
 ```bash
-make
+git clone https://gitlab.pasteur.fr/GIPhy/Concatenate.git
+```
+On computers with [GraalVM](hhttps://www.graalvm.org/downloads/) installed, a native executable can be built. In a command-line window, go to the _src_ directory, and type:
+```bash
+javac Concatenate.java 
+native-image Concatenate Concatenate
+rm Concatenate.class
 ```
-This will create the executable binary file `concatenate` that could be launched with the following command line model:
+This will create the native executable `Conctenate` that can be run with the following command line model:
 ```bash
-./concatenate [options]
+./Concatenate [options]
 ```
 
+
 ## Usage
 
 Launch _Concatenate_ without option to read the following documentation:
 
 ```
--i <infile>   To indicate the input file that contains containing every MSA file name (one 
-              per line). If the  character % is set before a file name,  the corresponding
-              MSA will be not used to  build the supermatrix of characters.  Each MSA file
-              should contain one MSA  (DNA, RNA,  amino acid, O1, ...)  in either FASTA or
-              PHYLIP format. Relative/absolute path is allowed for each MSA file (default:
-              datafiles.txt).
--o <outfile>  To set the output file name (default: supermatrix.phy or supermatrix.fasta)
--f            To write the supermatrix of characters in FASTA format (default: PHYLIP)
--l <integer>  To set the maximum length of the written sequences (default: infinity); when 
-              option -f is not set, this option leads to a PHYLIP-interleaved ouput file 
+ Concatenate
+
+ USAGE:   Concatenate  [-i <infile>]  [-o <outfile>]  [-f]  [-l <integer>]
+
+ where options are:
+
+ -i <infile>   to indicate the input file that contains containing every MSA file name (one
+               per line). If the  character % is set before a file name,  the corresponding
+               MSA will be not used to  build the supermatrix of characters.  Each MSA file
+               should contain one MSA  (DNA, RNA,  amino acid, O1, ...)  in either FASTA or
+               PHYLIP format. Relative/absolute path is allowed for each MSA file (default:
+               datafiles.txt).
+ -o <outfile>  To set the output file name (default: supermatrix.phy or supermatrix.fasta)
+ -f            To write the supermatrix of characters in FASTA format (default: PHYLIP)
+ -l <integer>  To set the maximum length of the written sequences (default: infinity); when 
+               option -f is not set, this option leads to a PHYLIP-interleaved ouput file 
+
 ```
 
 ## Notes
diff --git a/src/Concatenate.java b/src/Concatenate.java
index 8300d000775309211b2ae91519f9b28793a11fa9..856b1b7a1c575ede0850af95d044a7298fcff7e1 100644
--- a/src/Concatenate.java
+++ b/src/Concatenate.java
@@ -1,31 +1,30 @@
 /*
-  ####################################################################
-  Concatenate: building a supermatrix  of characters by  concatenating
-               a set of multiple sequence alignment
+  ########################################################################################################
 
-  Copyright (C) 2018  Alexis Criscuolo 
-
-  This program is free software: you can redistribute it and/or modify
-  it under the terms of the GNU General Public License as published by
-  the Free Software Foundation,  either version 3  of the License,  or
+  Concatenate: building a supermatrix of characters by concatenating a set of multiple sequence alignment
+  
+  Copyright (C) 2018-2020  Institut Pasteur
+  
+  This program  is free software:  you can  redistribute it  and/or modify it  under the terms  of the GNU
+  General Public License as published by the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
   
-  This program is distributed in the hope that it will be useful,  but
-  WITHOUT  ANY  WARRANTY;   without  even  the   implied  warranty  of
-  MERCHANTABILITY or  FITNESS FOR  A PARTICULAR  PURPOSE.  See the GNU 
-  General Public License for more details.
+  This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY;  without even
+  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+  License for more details.
   
-  You should have  received a copy  of the GNU  General Public License
-  along with this program. If not, see <http://www.gnu.org/licenses/>.
-
-  Contact: 
-  Institut Pasteur
-  Bioinformatics and Biostatistics Hub
-  C3BI, USR 3756 IP CNRS
-  Paris, FRANCE
+  You should have received a copy of the  GNU General Public License along with this program.  If not, see
+  <http://www.gnu.org/licenses/>.
+  
+  Contact:
+   Alexis Criscuolo                                                            alexis.criscuolo@pasteur.fr
+   Genome Informatics & Phylogenetics (GIPhy)                                             giphy.pasteur.fr
+   Bioinformatics and Biostatistics Hub                                 research.pasteur.fr/team/hub-giphy
+   USR 3756 IP CNRS                          research.pasteur.fr/team/bioinformatics-and-biostatistics-hub
+   Dpt. Biologie Computationnelle                     research.pasteur.fr/department/computational-biology
+   Institut Pasteur, Paris, FRANCE                                                     research.pasteur.fr
 
-  alexis.criscuolo@pasteur.fr
-  ####################################################################
+  ########################################################################################################
 */
 
 import java.io.*;
@@ -34,8 +33,9 @@ import java.util.*;
 public class Concatenate {
 
     // constants
+    final static String VERSION = "0.1b.201024ac";
     final static String MISSING = "????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????"; // one thousand unknown character states
-    final static String BLANK = "                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        "; // one thousand blank characters
+    final static String BLANK =   "                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        "; // one thousand blank characters
     final static String NO_FILE = "n.o.f.i.l.e";
 
     // options
@@ -70,11 +70,13 @@ public class Concatenate {
 	// ###########################
 	if ( args.length < 2 ) {
 	    System.out.println("");
-	    System.out.println(" USAGE:   Concatenate [options]");
+	    System.out.println(" Concatenate v." + VERSION + "                      Copyright (C) 2019-2020  Institut Pasteur");
+	    System.out.println("");
+	    System.out.println(" USAGE:   Concatenate  [-i <infile>]  [-o <outfile>]  [-f]  [-l <integer>]");
 	    System.out.println("");
 	    System.out.println(" where options are:");
 	    System.out.println("");
-	    System.out.println(" -i <infile>   To indicate the input file that contains containing every MSA file name (one ");
+	    System.out.println(" -i <infile>   to indicate the input file that contains containing every MSA file name (one");
 	    System.out.println("               per line). If the  character % is set before a file name,  the corresponding");
 	    System.out.println("               MSA will be not used to  build the supermatrix of characters.  Each MSA file");
 	    System.out.println("               should contain one MSA  (DNA, RNA,  amino acid, O1, ...)  in either FASTA or");
diff --git a/src/Makefile b/src/Makefile
deleted file mode 100644
index 5f1dc3945706c60deef43737cc3dd2d82ebdbbff..0000000000000000000000000000000000000000
--- a/src/Makefile
+++ /dev/null
@@ -1,8 +0,0 @@
-GCJ=gcj
-GCJFLAGS=-fsource=1.6 -march=native -msse2 -O3 -minline-all-stringops -fomit-frame-pointer -momit-leaf-frame-pointer -fstrict-aliasing -fno-store-check -fno-bounds-check -funroll-all-loops -Wall 
-OTHERFLAGS=-funsafe-math-optimizations -ffast-math
-MAIN=Concatenate
-EXEC=concatenate
-
-Concatenate: Concatenate.java
-	$(GCJ) $(GCJFLAGS) --main=$(MAIN) $(MAIN).java -o $(EXEC)