SERVICE RECOMMENDED LETTER MOS 15-OCT-2012 SL 737-SL-38-019 VACUUM WASTE SYSTEM MAINTENANCE RECOMMENDATIONS. SERVICE LETTER RECOMMENDED MOS ZS-JUL-1997 - (s) SL 737-SL-38-019 REV. A VACUUM WASTE SYSTEM MAINTENANCE RECOMMENDATIONS (SUPERSEDED BY SL 737-SL-38-019 REV. B). SERVICE SUPERSEDED LETTER