In order to give rise to priority all the essential elements, i.e. features of the invention in the priority document must be either expressly disclosed or directly and unambiguously implied by the text as filed. The question therefore arises as to what constitutes the essential elements, i.e. features of the invention, claimed in the European patent application, and whether or not these features are disclosed in the respective priority documents (cf. Art. 88(4) EPC 1973; see also T 81/87, OJ 1990, 250; T 65/92, T 127/92, T 296/93, T 479/97, T 342/98 and T 188/97). Essential elements missing in the priority document and recognised as essential only later on, are not part of the disclosure of the previous application and there is then no right to priority (T 81/87, OJ 1990, 250; T 301/87, OJ 1990, 335; T 269/87, T 296/93, T 1228/01). The "essential features" within the meaning of this jurisprudence are not the counterpart to the "non-essential features" within the meaning of T 73/88 ("Snackfood", OJ 1992, 557) decision. Accordingly, the jurisprudence based on T 81/87 has been upheld even after the opinion given in G 2/98 (see, for instance, T 479/97).