Some changes.

bibliography.bib

@@ -97,6 +97,16 @@
     annote = {A primary source, written by Horsford.}
 }
 
+% https://digital.sciencehistory.org/works/2227mq61j
+@book{HorsCook77,
+    author = {Eben Norton Horsford},
+    title = {Horsford's Cook Book},
+    year = {1877},
+    publisher = {Rumford Chemical Works},
+    address = {Providence, Rhode Island},
+    annote = {Primary source.}
+}
+
 % https://archive.org/details/discoveryofameri00hors/page/n9/mode/2up?ref=ol&view=theater
 @book{HorsDisc87,
     author = {Eben Norton Horsford},
@@ -139,6 +149,16 @@
     volume = {1},
     year = {1889},
     publisher = {Houghton, Mifflin and Company},
-    address = {Boston, Massachusetts}
+    address = {Boston, Massachusetts},
+    annote = {Primary source.}
 }
 
+% https://archive.org/details/discoveryofancie01hors/page/n21/mode/2up
+@book{HorsDisc90,
+    author = {Eben Norton Horsford},
+    title = {The Discovery of the Ancient City of Norumbega},
+    year = {1890},
+    publisher = {Houghton, Mifflin and Company},
+    address = {Boston, Massachusetts},
+    annote = {Primary source.}
+}