For corpus title "Atomium", pick 3 words appear in the title and calculate the total occurence of these words.
total occurrences refers to sum(occurrences)
SELECT T1.word, T1.occurrences FROM words AS T1 INNER JOIN pages_words AS T2 ON T1.wid = T2.wid WHERE T2.pid = ( SELECT pid FROM pages WHERE title = 'Atomium' ) LIMIT 3