5 It ain't necessarily so from Porgy and Bess / George Gershwin It ain't necessarily so from Porgy and Bess It ain't necessarlly so from Porgy and Bess It Ain't Necessarily So from Porgy and Bess It Ain't Necessarily So from Porgy and Bess; Summertime (from Porgy and Bess) / George Gershwin It Ain't Necessarily So (from Porgy and Bess) It Ain't Necessarilu So from Porgy and Bess It Ain't Necessarily So(From Porgy And Bess)2 并非必需