Besides εἰδῶ (οἶδα) and ἑστήκῃ, etc., Attic prose has only about 16 occurrences of the simple perf. subj., and from the following verbs only: βαίνω, δέδια, ἐγείρω, ἔοικα, θνῄσκω, λαμβάνω, λανθάνω, πάσχω, ποιῶ, φύ_ω. Hippocr. has forms from βιβρώσκω, πονῶ, τεύχω. There are about 30 occurrences in the
poetry. Attic prose writers show about 25 cases of the periphrasis from all ω-verbs.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].