diff --git a/solutions/chap01soln.ipynb b/solutions/chap01soln.ipynb
index 1d9e9386b..7f0c4dd4c 100644
--- a/solutions/chap01soln.ipynb
+++ b/solutions/chap01soln.ipynb
@@ -617,7 +617,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Select the `birthord` column, print the value counts, and compare to results published in the [codebook](http://www.icpsr.umich.edu/nsfg6/Controller?displayPage=labelDetails&fileCode=PREG&section=A&subSec=8016&srtLabel=611933)"
+    "Select the `birthord` column, print the value counts, and compare to results published in the [codebook](ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Dataset_Documentation/NSFG/Cycle6Codebook-Pregnancy.pdf)"
    ]
   },
   {
@@ -683,7 +683,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Select the `prglngth` column, print the value counts, and compare to results published in the [codebook](http://www.icpsr.umich.edu/nsfg6/Controller?displayPage=labelDetails&fileCode=PREG&section=A&subSec=8016&srtLabel=611931)"
+    "Select the `prglngth` column, print the value counts, and compare to results published in the [codebook](ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Dataset_Documentation/NSFG/Cycle6Codebook-Pregnancy.pdf)"
    ]
   },
   {
diff --git a/solutions/chap02soln.ipynb b/solutions/chap02soln.ipynb
index f63883fc4..c38d5ac8c 100644
--- a/solutions/chap02soln.ipynb
+++ b/solutions/chap02soln.ipynb
@@ -851,7 +851,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Make a histogram of <tt>totincr</tt> the total income for the respondent's family.  To interpret the codes see the [codebook](http://www.icpsr.umich.edu/nsfg6/Controller?displayPage=labelDetails&fileCode=FEM&section=R&subSec=7876&srtLabel=607543)."
+    "Make a histogram of <tt>totincr</tt> the total income for the respondent's family.  To interpret the codes see the [codebook](ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Dataset_Documentation/NSFG/Cycle6Codebook-Pregnancy.pdf)."
    ]
   },
   {