diff --git a/R/association-scores.R b/R/association-scores.R
index 526ebab..8c79295 100644
--- a/R/association-scores.R
+++ b/R/association-scores.R
@@ -107,7 +107,7 @@
 #' Dunning, T. (1993): Accurate methods for the statistics of surprise and coincidence. Comput. Linguist. 19, 1 (March 1993), 61-74.
 #'
 #' Evert, Stefan (2004): The Statistics of Word Cooccurrences: Word Pairs and Collocations. PhD dissertation, IMS, University of Stuttgart. Published in 2005, URN urn:nbn:de:bsz:93-opus-23714.
-#' Free PDF available from <http://purl.org/stefan.evert/PUB/Evert2004phd.pdf>
+#' Free PDF available from <https://purl.org/stefan.evert/PUB/Evert2004phd.pdf>
 #'
 ll <- function(O1, O2, O, N, E, window_size) {
   r1 = as.double(O1) * window_size
diff --git a/man/association-score-functions.Rd b/man/association-score-functions.Rd
index 914d96c..97454fc 100644
--- a/man/association-score-functions.Rd
+++ b/man/association-score-functions.Rd
@@ -78,7 +78,7 @@
 Dunning, T. (1993): Accurate methods for the statistics of surprise and coincidence. Comput. Linguist. 19, 1 (March 1993), 61-74.
 
 Evert, Stefan (2004): The Statistics of Word Cooccurrences: Word Pairs and Collocations. PhD dissertation, IMS, University of Stuttgart. Published in 2005, URN urn:nbn:de:bsz:93-opus-23714.
-Free PDF available from \url{http://purl.org/stefan.evert/PUB/Evert2004phd.pdf}
+Free PDF available from \url{https://purl.org/stefan.evert/PUB/Evert2004phd.pdf}
 }
 \seealso{
 Other collocation analysis functions: