^
Dyremose, Jeanette & Lars (2003). Det levende bælgspil : det kunstneriske harmonikaspils forudsætning (in Danish). Dyremose.com. p. 133. ISBN87-988128-1-5. automatically coupled chords on the bass side
^US application 2845831, Laurens Hammond, "Keyboard and switching mechanism for electrical musical instruments", published 1958-08-05, assigned to Hammond Organ Company (filed 1953-02-05, priority date:1950-06-23). "This application is a division of my copending application Serial No. 169,902, filed June 23, 1950, which was abandoned after this application was filed."
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