Update docs/examples/example_survival.ipynb

Co-authored-by: Kevin Klein <[email protected]>

docs/examples/example_survival.ipynb

@@ -11,7 +11,7 @@
     "\n",
     "## Loading the data\n",
     "\n",
-    "First we will load the data. For this example we will use a dataset from Rossi et al. - Money, Work and Crime (1980). The data pertain to 432 convicts who were released from Maryland state prisons in the 1970s and who were followed up for one year after release. Half the released convicts were assigned at random to an experimental treatment in which they were given financial aid; half did not receive aid."
+    "First we will load the data. For this example we will use a dataset from [Rossi et al. - Money, Work and Crime (1980)](https://gwern.net/doc/sociology/1980-rossi-moneyworkandcrime.pdf). The data describes 432 convicts who were released from Maryland state prisons in the 1970s and who were observed for one year after release. Half the released convicts were assigned at random to an experimental treatment in which they were given financial aid; half did not receive aid."
    ]
   },
   {