1. Sources:
2. Pliny Nat. Caius Plinius Secundus, Historia Naturalis (Pliny the Elder, The Natural History, John Bostock, M.D., F.R.S., H.T. Riley, Esq., B.A., Ed. - Perseus Digital Library - https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.02.0137 - retrieved 30.10.2021).
3. Vitruvius Arch. Vitruvius Pollio, De architectura (Vitruvius Pollio, The Ten Books on Architecture, Morris Hicky Morgan, Ed. - Perseus Digital Library - https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.02.0073 - retrieved 30.10.2021).
4. References:
5. Adam 2005 - J. P. Adam, Roman Building materials and techniques, London 2005.