Cite the PostScript Language Reference by its public URL

crates/eps/src/import/interp.rs

@@ -106,7 +106,7 @@ impl<'a> Interp<'a> {
         let made = super::obj::track();
         let system = new_dict();
         // The standard encodings are also instances of the Encoding category, the same arrays
-        // (PLRM 3rd ed., `findencoding` and §3.9.2).
+        // (PLRM 3rd ed., §3.9.2 and `findencoding`, <https://www.adobe.com/jp/print/postscript/pdfs/PLRM.pdf>).
         let encodings = new_dict();
         {
             let mut d = system.borrow_mut();

crates/eps/src/import/tests.rs

@@ -893,8 +893,8 @@ fn the_generic_category_defines_new_categories() {
 }
 
 /// The standard encodings are instances of the Encoding category, the same arrays as the names in
-/// `systemdict` (PLRM 3rd ed., `findencoding` and §3.9.2). Ghostscript's `eps2write` finds
-/// `StandardEncoding` that way for the fonts it embeds.
+/// `systemdict` (PLRM 3rd ed., §3.9.2 and `findencoding`, <https://www.adobe.com/jp/print/postscript/pdfs/PLRM.pdf>).
+/// Ghostscript's `eps2write` finds `StandardEncoding` that way for the fonts it embeds.
 #[test]
 fn the_standard_encodings_are_encoding_resources() {
     check("/StandardEncoding /Encoding findresource StandardEncoding eq");