Add reference to particlezoo

Author: meevans1

Diff for: 13-TeV-examples/uproot_python/HZZAnalysis.ipynb

@@ -20,7 +20,9 @@
     "\n",
     "Then, the amount of $ZZ \\rightarrow \\ell\\ell\\ell\\ell$ is reduced, whilst keeping $H \\rightarrow ZZ \\rightarrow \\ell\\ell\\ell\\ell$ signal\n",
     "\n",
-    "The datasets used in this notebook have already been filtered to include at least 4 leptons per event, so that processing is quicker."
+    "The datasets used in this notebook have already been filtered to include at least 4 leptons per event, so that processing is quicker.\n",
+    "\n",
+    "Feynman diagram pictures are borrowed from our friends at https://www.particlezoo.net"
    ]
   },
   {

Diff for: 13-TeV-examples/uproot_python/HyyAnalysis.ipynb

@@ -14,7 +14,9 @@
     "# How to rediscover the Higgs boson yourself!\n",
     "This notebook uses ATLAS Open Data http://opendata.atlas.cern to show you the steps to rediscover the Higgs boson yourself!\n",
     "\n",
-    "The datasets used in this notebook have already been filtered to include at least 2 photons per event, so that processing is quicker."
+    "The datasets used in this notebook have already been filtered to include at least 2 photons per event, so that processing is quicker.\n",
+    "\n",
+    "Feynman diagram pictures are borrowed from our friends at https://www.particlezoo.net"
    ]
   },
   {