https://en.wikipedia.org/wiki/I_Saw_Three_Ships
http://cantorion.org/music/146/I-Saw-Three-Ships-Voice
https://www.flutetunes.com/tunes/i-saw-three-ships.pdf
http://www.hymnsandcarolsofchristmas.com/Hymns_and_Carols/i_saw_three_ships.htm
http://www0.cpdl.org/wiki/index.php/I_saw_three_ships_come_sailing_in_(Traditional)