Give free source for Quinn paper

* leapseconds.awk, zic.8: Mention the NIST-distributed
copy of the Quinn paper, too.

leapseconds.awk

@@ -20,7 +20,10 @@ BEGIN {
   print "# periodically uses leap seconds to keep UTC to within 0.9 s of UT1"
   print "# (which measures the true angular orientation of the earth in space); see"
   print "# Terry J Quinn, The BIPM and the accurate measure of time,"
-  print "# Proc IEEE 79, 7 (July 1991), 894-905 <http://dx.doi.org/10.1109/5.84965>."
+  print "# Proc IEEE 79, 7 (July 1991), 894-905 <http://dx.doi.org/10.1109/5.84965>,"
+  print "# reprinted in: Hackman C, Sullivan DB (eds), Time and frequency measurement,"
+  print "# American Association of Physics Teachers (1996),"
+  print "# <http://tf.nist.gov/general/pdf/1168.pdf>, 75-86."
   print "# There were no leap seconds before 1972, because the official mechanism"
   print "# accounting for the discrepancy between atomic time and the earth's rotation"
   print "# did not exist until the early 1970s."

zic.8

@@ -463,7 +463,10 @@ if a second was skipped.
 .\" than one leap second to be inserted or deleted at a time.
 .\" The C Standard is in error in suggesting the possibility.
 .\" See Terry J Quinn, The BIPM and the accurate measure of time,
-.\" Proc IEEE 79, 7 (July 1991), 894-905.
+.\" Proc IEEE 79, 7 (July 1991), 894-905, reprinted in
+.\" Hackman C, Sullivan DB (eds), Time and frequency measurement,
+.\" American Association of Physics Teachers (1996),
+.\" <http://tf.nist.gov/general/pdf/1168.pdf>, 75-86."
 .\"	or
 .\"	.q ++
 .\"	if two seconds were added