"A detailed and path-breaking analysis (HOPKINS 1896a) shows large categories of words found in the Late books (1,8,9,10, and often 5), but missing in the Early (6,3,7) and Middle books (4,2) except in a few stray hymns classified by the western academic scholars as Late or interpolated hymns within these books. These include such categories as words pertaining to ploughing or to other paraphernalia of agriculture, words associated with certain occupations and technologies (and even with what could be interpreted as the earliest references to the castes), words where the r is replaced by l (playoga and pulu for prayoga and puru), a very large number of personal names (not having to do with the name types, common to the Rigveda, Avesta and Mitanni records, analyzed by me), various suffixes and prefixes used in the formation of compound words, certain mythical or socio-religious concepts (Sūrya as an Āditya, Indra identified with the Sun, the discus as a weapon of Indra and the three-edged or three-pointed form of this weapon, etc), various grammatical forms (cases of the resolution of the vowel in the genitive plural of ā stems, some transition forms common in later literature, the Epic weakening of the perfect stem, the adverb adas, etc.), particular categories of words (Soma epithets like madacyuta, madintara/madintama, the names of the most prominent meters used in the Rigveda, etc.), certain stylistic peculiarities (the use of reduplicated compounds like mahāmaha, calācala, the use of alliteration, the excessive use of comparatives and superlatives, etc.), and many, many more."