See Footnotes in Books in a Popup Window
Notice in your Bibles the green letters and numbers that appears inline with the Biblical text. These "popups" are the footnotes and cross references that normally appear in the print editions. Rest your cursor on green text to see the information in a pop up window. Click the green text to make the Bible cross references "hot". Now rest your cursor on a "hot" Bible reference to see the passage in a pop up window.