1. Seneca LA. Naturales Quaestiones [Research on Nature]. Liber I, Chapt 6. Circa 62 CE. (Latin)
2. Sobre el origen de los anteojos [On the origin of spectacles];Murube;Studium ophthalmologicum,1983
3. Letter to H. Oldenburg, Secretary of the Royal Society of London, 17th September 1683;van Leeuwenhoek;Philosophical Transactions,1684
4. Virgil. The georgics. Book IV. 29 BCE. (Latin)
5. Quoted by Emerton NE. Creation in the thought of J.B. van Helmont and Robert Fludd;van Helmont,1994