European green woodpecker hole is excavated in a tree; four to six eggs are laid which hatch after 19–20 days. The European green woodpecker measures 30–36 cm in length with a 45–51 cm wingspan. Both sexes are green above and pale yellowish green below, with yellow rump and red crown and nape; the moustachial stripe has a red centre in the male but is solid black in the female. The lores and around the white eye are black in both male and female, except in the Iberian race "P. v." subsp. "sharpei", in which it is dark grey and males have only a
An Essay on the Nature and Significance of Economic Science on economic methodology in generating a range of tightly-argued, radical implications from a simple definition, for example in admitting an "aspect" of behaviour (rather than a list of behaviours) but not limiting the subject-matter of economics, provided that the influence of scarcity impinges on these (pp. 16–17). The broad behavioural definition is credited for its consistency with the expanding boundaries of economics decades later. In this Robbins both narrows the definition of economics, thereby demonstrating the usefulness of deduction, and opens up the subject-matter of economics. Robbins's "Essay" is one of the most-cited works on the methodology and philosophy of