International law — Relation to municipal law — Interpretation of double taxation agreement — Agreed interpretation communicated to tax authorities in ministerial instructions — Whether agreed interpretation binding on municipal courts — Double Taxation Agreement between Austria and Switzerland, 1953 — The law of Austria.

Treaties — Special kinds of — Double taxation agreements — Interpretation of — Agreed interpretation communicated to tax authorities in ministerial instructions — Whether agreed interpretation binding on municipal courts — Double Taxation Agreement between Austria and Switzerland, 1953 — “Regular frontier travellers” — The law of Austria.