Kaicheng (919) — the same event in Goryeosa Jeolyo, Samguk Sagi and Samguk Yusa

Goryeosa Jeolyo: Makes his capital south of Songak, raising Songak County to Gaeju and establishing markets, wards, five districts and six guards…

What each source says

Goryeosa Jeolyo (Essentials of Goryeo History) · AD 919 · 開城

Makes his capital south of Songak, raising Songak County to Gaeju and establishing markets, wards, five districts and six guards

定都于松嶽之陽。
Location: 권1 太祖神聖大王 二年

Samguk Sagi (History of the Three Kingdoms) · AD 919 · 개성

Taejo moved the capital to Songak district.

我太祖移都松岳郡。
Location: 卷12 景明王 3年

Samguk Yusa (Memorabilia of the Three Kingdoms) · AD 919 · Gaeseong

Taejo moved the capital to Songak district (in this year ten temples, including Beopwangsa and Jaunsa, were built).

己卯移都松岳郡
Location: 王曆

Place: 開京

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