Figure 1.

Main screen of PrUnAs application. From left to right, in rows, the titles in English are: The electric car; Catalan economy in the nineteenth century; Chemical elements; Volcanoes; The infinity; Infectious diseases; Non-formal education; Cubist art; Artificial intelligence; Wind instruments; Seven tourist destinations; Human rights in the twentieth century; Olympic games in Seoul; Gothic buildings; Poets from the 27th; Western cinema; The Red Cross; Colour TV; D-day; Security corps; Reproduction of lions; The sun at North Cape; Romanic languages; Elections at the USA; Newton’s laws; Rationalism in Philosophy; Human memory; Photosynthesis.