Frederick William Lanchester, Aircraft in Warfare — Chapter VI (1916)
“ Individual value of Ships or Units. The factor the most difficult to assess in the evaluation of a fleet as a fighting machine is (apart from the personnel) the individual value of its units, when these vary amongst themselves. There is no possibility of entirely obviating this difficulty, since the fighting value of any given ship depends not only upon its gun armament, but also upon its protective armour. ”
