replace in opening quotations

node113.html

@@ -137,7 +137,7 @@ a delay of <IMG
  SRC="img783.png"
  ALT="$x[n-1.5]$">.
 We could do this using standard four-point interpolation, putting a cubic
-polynomial through the four ``known" points (0, x[n]), (1, x[n-1]), (2, x[n-2]),
+polynomial through the four "known" points (0, x[n]), (1, x[n-1]), (2, x[n-2]),
 (3, x[n-3]), and then evaluating the polynomial at the point 1.5.  Doing
 this repeatedly for each value of <IMG
  WIDTH="13" HEIGHT="13" ALIGN="BOTTOM" BORDER="0"