From the site you gave the address for, Q:

"In the 50s, American folk singer Pete Seeger (1919 - ) often sang at college concerts. In 1958, en route to one of these concerts, on the plane, he had his inspiration for "Where Have All the Flowers Gone?". Seeger pulled out his pocket-size song notebook and as he recalls, "Leafing through it, I came across three lines I'd written down, oh, at least a year or two before". Seeger had read a novel by Mikhail Sholokhov, And Quiet Flows the Don, where he noted the three lines came from a Ukrainian folk song."

Just when the world was seeming to be simple . . . .