《明史·列传·卷一百零二》
杨博认为蓟州近临京都，护卫京都地区和皇族陵寝为大，分遣众将，划地设防。
博以蓟逼京师，护畿甸陵寝为大，分布诸将，画地为防。
Yang Bo thought that Jizhou was close to the capital and thus of great importance to protect the capital area and the imperial tombs, and he sent his generals to different areas to be responsible for defense.