Template talk:vo-decl-noun

Predicative case

• Schleyer's Volapük doesn't have it.
• The unreliable source http://volapük.com/foms-gramatik.html (on http://volapük.com by w:en:Ralph Midgley and w:en:Michael Everson) claims that the predicative goes back to w:en:Arie de Jong, though it also states that the summary is based on ""An Introduction to Volapük" by Ed Robertson", which is based on a course by w:en:Ralph Midgley.
• predicative case has an unreliable usenet quote from 2005, claiming that de Jong added the predicative.
• The "Volapük nulik" materials of http://volapuk.temerov.org/Volapükanef/Deutänapük/gramats.php , sometimes have a predicative (Ed. Robertson's "Einführung in das Volapük" which states predicative only occurs in modern Volapük and is rarely used) and sometimes not (e.g. "Kurze Volapük-Grammatik", Johann Schmidt's "Lehrbuch der Weltsprache Volapük").
• Arie de Jong's "Gramat Volapüka" only gives five cases, including vocative but without predicative: Google Books' preview (nominatif, genitif, datif, kusatif, vokatif = nominative, dative, accusative, vocative; subyet, predikat = subject, predicate).

Thus it appears that the predicative doesn't occur in Schleyer's Volapük, in de Jong's New Volapük, but in Midgley's, Robertson's and Everson's New New Volapük. And furthermore, Schleyer's grammar and de Jong's grammar were published as books and are reliable sources, while Midgley's, Robertson's and Everson's maybe were only published in the net.
So:

• Where does the predicative come from?
• Are there reliable sources for it, like printed and published books (cp. WT:CFI#Attestation)?

--14:18, 24 September 2018 (UTC)