JEs

Seems broader than just reference book.

@@ -15,3 +15 @@
-</sense>
-<sense>
-<pos>&n;</pos>
+<gloss>study-aid book</gloss>
@@ -18,0 +17 @@
+<gloss>student handbook</gloss>

I'm not entirely sure where to get a good reference for this, but essentially: I think the current lone meaning is misleading as few people would think of supplemental school textbooks, which are definitely often meant in Japanese, as "reference books" even if this might technically apply to them — I imagine some guide to metallurgy in the 15th century or dictionary or whatever. Take a look at the google image results for "reference book" and 参考書 for some more proof. Certainly the Japanese term also includes the "reference book" meaning, though, so I keep both. I use "supplemental" because there does seem to be a difference to 教科書: https://chigai.site/2598/

@@ -15,0 +16,4 @@
+<sense>
+<pos>&n;</pos>
+<gloss>supplemental textbook</gloss>
+</sense>