1. Bach GL (1980) Economics. An introduction to analysis and policy. Prentice-Hall, London
2. Blanchard O (2000) Macroeconomics. Prentice-Hall, London
3. Carnap R (1966) Physikalische Begriffsbildung, 2nd edn. Wissenschaftliche Buchgesellschaft Darmstadt, Darmstadt
4. Díez A (1997) A hundred years of numbers: a historical introduction to measurement theory part I: the formation period. Stud Hist Philos Sci 21:167–181
5. Guarino N (1998) Formal ontology in information systems. In: Guarino N (ed) 1st international conference on formal ontology in information systems (FOIS98). IOS Press, Trento, pp 3–15