diff --git a/README.md b/README.md
index 4578312..312c23f 100644
--- a/README.md
+++ b/README.md
@@ -63,6 +63,22 @@ Clone this repository and `cd` into it, then run
     mkdir ~/.cheat
     cp cheatsheets/* ~/.cheat
 
+### Testing
+
+After installing for all users or in your home directory, try `cheat tar` for instance.
+
+### Troubleshooting
+
+In case you got an error such as:
+> ImportError: No module named argparse
+
+You're probably using python < 2.7 and you need to manually install the argparse module.
+You can do this easily with pip:
+```bash
+sudo apt-get python-pip
+sudo pip install argparse
+```
+Other methods: https://pypi.python.org/pypi/argparse
 
 Modifying Cheatsheets
 =====================
diff --git a/cheatsheets/lsof b/cheatsheets/lsof
index ca08a02..607c1ca 100644
--- a/cheatsheets/lsof
+++ b/cheatsheets/lsof
@@ -1,3 +1,6 @@
+# List all ipv4 network files
+sudo lsof -i4
+
 # To find listening ports:
 lsof -Pnl +M -i4
 
diff --git a/cheatsheets/netstat b/cheatsheets/netstat
index 72fbc07..c479fae 100644
--- a/cheatsheets/netstat
+++ b/cheatsheets/netstat
@@ -9,3 +9,5 @@ netstat -pln | grep <port> | awk '{print $NF}'
 
 Example output: 1507/python
 
+# Fast display of ipv4 tcp listening programs
+sudo netstat -vtlnp --listening -4
diff --git a/cheatsheets/nmap b/cheatsheets/nmap
index 7620afd..68da56a 100644
--- a/cheatsheets/nmap
+++ b/cheatsheets/nmap
@@ -31,3 +31,6 @@ nmap -traceroute [target]
 # TCP ACK ping:   -PA
 # UDP ping:       -PU
 # ARP ping:       -PR
+
+# Example: Ping scan all machines on a class C network
+nmap -sP 192.168.0.0/24
diff --git a/cheatsheets/pdftk b/cheatsheets/pdftk
index d4d2ec2..6f1609c 100644
--- a/cheatsheets/pdftk
+++ b/cheatsheets/pdftk
@@ -1,6 +1,9 @@
 # Concatenate all pdf files into one:
 pdftk *.pdf cat output all.pdf
 
+# Concatenate specific pdf files into one:
+pdftk 1.pdf 2.pdf 3.pdf cat output 123.pdf
+
 # Concatenate pages 1 to 5 of first.pdf with page 3 of second.pdf
 pdftk A=fist.pdf B=second.pdf cat A1-5 B3 output new.pdf
 
diff --git a/cheatsheets/ps b/cheatsheets/ps
index 06dac71..3710a90 100644
--- a/cheatsheets/ps
+++ b/cheatsheets/ps
@@ -1,8 +1,11 @@
 # To list every process on the system:
 ps aux
 
+# To list a process tree
+ps axjf
+
 # To list every process owned by foouser:
 ps -aufoouser
 
 # To list every process with a user-defined format:
-ps -eo pid,user,command
\ No newline at end of file
+ps -eo pid,user,command
diff --git a/cheatsheets/sam2p b/cheatsheets/sam2p
new file mode 100644
index 0000000..9d5f9f9
--- /dev/null
+++ b/cheatsheets/sam2p
@@ -0,0 +1,2 @@
+# Concatenate all pdf files into one:
+sam2p *.pdf out.pdf