diff --git a/README.md b/README.md
index 1bd04f9..c37ad20 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,7 @@ paper to pdf converter suitable for texts.
     - [Coming soon](#coming-soon)
     - [Origin of the name](#origin-of-the-name)
     - [Troubleshooting](#troubleshooting)
+    - [Tested on](#tested-on)
     - [License](#license)
 
 [](TOC)
@@ -185,6 +186,9 @@ http://www.jpeek.com/articles/linuxmag/2006-08/
 - [GNU Parallel](http://www.gnu.org/software/parallel/)
   - Execute image post processing jobs in parallel
 
+- [GNU stream editor](https://www.gnu.org/software/sed/)
+  - Remove leading zeros from filenames
+
 - [Netpbm](http://netpbm.sourceforge.net/)
   - Fix the newly scanned immages by truncating the unnecessary parts. This
     is mostly useful when scanning from the ADF
@@ -227,11 +231,17 @@ This is the error returned by `convert`:
 
     convert: attempt to perform an operation not allowed by the security policy `PDF' @ error/constitute.c/IsCoderAuthorized/408.
 
+## Tested on
+
+| Distribution | Scanner Name | `vendor:product` | Connection | 
+|--------------|--------------|------------------|------------|
+| Parabola GNU/Linux-libre | HP Officejet 2620 | `03f0:c911` | USB |
+
 ## License
 
 ![https://www.gnu.org/graphics/gplv3-127x51.png](https://www.gnu.org/graphics/gplv3-127x51.png)
 
-Copyright (C) 2017-2018 frnmst (Franco Masotti)
+Copyright (C) 2017-2018 frnmst (Franco Masotti) <franco.masotti@live.com>
 
 spectrscan 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 
diff --git a/fbopt b/fbopt
index 82e3bce..1d3c43d 100644
--- a/fbopt
+++ b/fbopt
@@ -100,6 +100,7 @@ main()
     local resolution="${RESOLUTION}"
     local source="${SOURCE}"
     local unpaper="${UNPAPER}"
+    local two_sided="${TWO_SIDED}"
 
     local program_name="${0}"
     opts="$(getopt \
diff --git a/spectrscan b/spectrscan
index af5ed8a..1f00638 100755
--- a/spectrscan
+++ b/spectrscan
@@ -4,7 +4,6 @@
 # spectrscan
 #
 # Copyright (C) 2017-2018 frnmst (Franco Masotti) <franco.masotti@live.com>
-#                                                 <franco.masotti@student.unife.it>
 #
 # This file is part of spectrscan.
 #
@@ -34,12 +33,18 @@ check_software()
         pdftk \
         parallel \
         file \
-        pamfix
+        pamfix \
+        sed \
+        tr \
+        sort \
+        ls \
+        head
 }
 
 get_last_page_side_a()
 {
-    ls spectrscan_out*.pnm | sort --reverse | head -n1 | tr -d [a-z]._
+    # remove trailing zeros with sed.
+    ls spectrscan_out*.pnm | tr -d [a-z]._ | sed -e 's/^[0]*//' | sort --reverse --numeric | head -n1
 }
 
 select_page_parameters()
diff --git a/spectrscan.HP_Officejet_2620.conf b/spectrscan.HP_Officejet_2620.conf
index 7a48464..357a7b6 100644
--- a/spectrscan.HP_Officejet_2620.conf
+++ b/spectrscan.HP_Officejet_2620.conf
@@ -1,7 +1,9 @@
 TMP_DIR="$(pwd)/.spectrscan-$RANDOM"
 SRC_DIR="$(pwd)"
 IMAGEMAGICK='-normalize -level 70%,100%,1.0'
+#IMAGEMAGICK='-normalize -level 20%,100%,1.0'
 MODE='Lineart'
 RESOLUTION='300'
 SOURCE='ADF'
 UNPAPER='false'
+TWO_SIDED='false'