noun
authoritative sources
Refers to people or organizations considered reliable and official, often used in news reporting.
権威筋によると、新政策は来月発表される見込みだ。
According to authoritative sources, the new policy is expected to be announced next month.
Compound of 権威 (authority) and 筋 (source, line). The exact historical derivation is uncertain, but the combination naturally yields the meaning 'authoritative sources'.