Pursuant to R. 43(6) EPC claims shall not rely, "except where absolutely necessary", on references to the description or drawings in specifying the technical features of the invention. Expressions such as "as described in part...of the description", or "as illustrated in figure...of the drawings" are to be avoided.

In T 150/82 (OJ 1984, 309) the board ruled that claims relying on references to the description in the specification in respect of all their technical features (so called "omnibus claims") were unallowable as contrary to R. 29(4) and R. 29(6) EPC 1973 (R. 43(4) and (6) EPC), unless absolutely necessary, e.g. when a plurality of conditions would not lend themselves to verbal expression without such a reference. Examples of such exceptions included inventions containing features or limitations which could only be expressed by means of drawings or graphs defining a particular shape or a plurality of conditions. In T 271/88 the board upheld T 150/82 and decided that it was not possible to base claims on an appendix showing structural chemical formulae designated as "chemical formulae incorporated within claims". The board held that it was quite evident that the terms "description" and "drawing" in R. 29(6) EPC 1973 were meant to cover structural chemical formulae. See also T 752/94.

In T 1156/01 the board considered that, if the invention was characterised by parameters, the method of and means for measurement should appear completely in the claim itself, whenever this was reasonable, or by reference to the description in accordance with R. 29(6) EPC 1973, if the method was so long that it would impair the conciseness of the claim (confirmed in T 796/01).

In T 237/84 (OJ 1987, 309) the board stated that the purpose of reference signs in a claim (R. 29(7) EPC 1973) was to make the claims easier to understand. They did not limit the scope of the claim but did affect its clarity and might enable it to be expressed more concisely than would otherwise be possible (confirmed e.g. in T 572/90). In T 986/97 the board allowed a reference to the drawings.

In decision T 816/90 plasmids were defined by use of a designation which had no technical meaning per se. Moreover, their structure was defined by reference to a figure. The board was of the opinion that such a definition of a plasmid was contrary to the requirements of Art. 84 EPC 1973 and therefore could not be accepted.