FIRST AND SECOND PERFECT (AND PLUPERFECT) ACTIVE Indicative.—The perfect of τίθημι is τέθηκα. A later form τέθεικα, not found on Attic inscriptions till after 200 B.C. and due to the analogy of εἷκα, still appears in some texts. τέθεκα is Doric. For καθέστακα Attic used καταστήσα_ς ἔχω (cp. cross599 b).
a. The dual and plural of the second perfect and pluperfect of ἵστημι ( cross417) are formed without κ: ἕστατον, ἕσταμεν (without augment in the pluperf.), ἑστᾶσι from ἑ-στα-αντι, pluperf. ἕστα-σαν. The singular is supplied by the 1 perf. ἕστηκα
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].