F‑IV, 3.7 Alternatives in a claim - Guidelines for Examination
Alternatives in a claim 

A claim, whether independent or dependent, may refer to alternatives, provided that the number and presentation of alternatives in a single claim does not make the claim obscure or difficult to construe and provided that the claim meets the requirements of unity (see also F‑V, 4 and 9). In case of a claim defining (chemical or non-chemical) alternatives, i.e. a so-called "Markush-grouping", unity of invention should be considered to be present if the alternatives are of a similar nature and can fairly be substituted for one another (see F‑V, 5).

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