2 services carry this tag in their source record. Tags come from the provider, not from us — a tag is a claim about what the service does, not proof that it does it well.
HTTP 501 Not Implemented: what it means (method unsupported by server), what a client should do (do not retry), the class it belongs to, whether it is retryable and idempotency-safe, the defining RFC, and common causes....
Composite due-diligence profile of a US 501(c) nonprofit by EIN or name: identity (name, EIN, decoded NTEE, subsection, foundation type, ruling date), current IRS status fusion (Pub 78 deductibility, auto-revocation, exe...