Calendar Clarification: the Beach Boys and recording of "God Only Knows"

There are all kinds of dates thrown around the Internet about the recording of "God Only Knows" by the Beach Boys, with some websites claiming the Beach Boys recorded the song on March 6, others on March 9, others on March 10, and others on April 11.  Keith Badman and Tony Bacon, in their book The Beach Boys:  The Definitive Diary of America's Greatest Band, on Stage and in the Studio, states that the group recorded a first instrumental track on March 8, a second on March 9, and the vocal recording was made on March 10.  Books are usually outstanding sources, since an editor and publisher have to also sign off on the facts presented within.  In this case, we believe Badman and Bacon are wrong in this instance.  The famous group of backing musicians known as The Wrecking Crew gathered for 20 takes on March 10, with vocal overdubbing done on April 11, according to the book Fifty Sides of the Beach Boys:  The Songs That Tell Their Story by Matt Dillon.  This date is confirmed by Kent Hartman, in his 2012 book The Wrecking Crew:  The Inside Story of Rock and Roll's Best-Kept Secret.  Hartman's book lists one and only one recording session for The Wrecking Crew:  March 10.  It is inaccurate to say the Beach Boys recorded the song on any one day, but rather, they began recording on March 10, and finished April 11.