[国外标准] BS 8521-2009 Specification for dual-tone multi-frequency (—TMF) signalling protocol for social alarm
[国外标准] JIS Z 8521：1999 Ergonomics -- Office work with visual display terminals (VDTs)-- Guidance on usabili
[国家标准] GB 8521-1987 钢筋切断机
[机械行业标准] JB/T 8521-1997 起重吊具 合成纤维吊装带