Which permanent account has registration of invite-only and userpics free of unknown?
CREATE TABLE "defunct_sites" (
  "name" text,
  "year_began" text,
  "registration" text,
  "userpics_free" text,
  "userpics_paid" text,
  "monthly_cost_for_paid_account" text,
  "yearly_cost_for_paid_account" text,
  "permanent_account" text
);
SELECT "permanent_account" FROM "defunct_sites" WHERE "userpics_free"='unknown' AND "registration"='invite-only';