What is the abbreviation for American century livestrong income mutual funds usmf?

Looking for the shorthand of American century livestrong income mutual funds usmf or how to abbreviate it? We have 5 shorthands for American century livestrong income mutual funds usmf.

ARTAX — American Century Livestrong Income (Mutual Funds [USMF])
ARTOX — American Century Livestrong Income (Mutual Funds [USMF])
ARSRX — American Century Livestrong Income (Mutual Funds [USMF])
ATTCX — American Century Livestrong Income (Mutual Funds [USMF])
ATTIX — American Century Livestrong Income (Mutual Funds [USMF])