diff --git a/code/reference/ch_wireshark/TCPFlowControlDemo/client.py b/code/reference/ch_wireshark/TCPFlowControlDemo/client.py
index de8f653..d500a28 100644
--- a/code/reference/ch_wireshark/TCPFlowControlDemo/client.py
+++ b/code/reference/ch_wireshark/TCPFlowControlDemo/client.py
@@ -1,5 +1,5 @@
 import socket
-import time
+import time  
 
 ip_port = ("server", 9999)
 data = "0123456789\n"*100
diff --git a/figure/chapters/wireshark/arp-format.pdf b/figure/chapters/wireshark/arp-format.pdf
new file mode 100644
index 0000000..dd9b4e8
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diff --git a/figure/chapters/wireshark/arp-format.png b/figure/chapters/wireshark/arp-format.png
deleted file mode 100644
index fde08c0..0000000
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