1. Pohle, G. and Frenking, H., ‘Criteria for the Evaluation of the Mixture’s Uniformity’ (only available in German), Research Report (Federal Ministry of Transport, 1978).
2. Hummel, A., ‘The Concrete ABC’ (only available in German), 12th Edn. (Berlin, 1959),
3. Losinger, R., ‘Measurement of the wet concrete’s workability (only available in German), PhD Thesis (Rösch, Vogt & Co., bern, 1956).
4. Papadakis, M., ‘Relevance of fine basic materials in rheology of wet concrete’, 4th International Congress of the Precast Concrete Block Industry, Paris, Apr. (1963).
5. Forschungsgesellschaft für das Straßenwesen, ‘Quality Guidelines for Concrete Mixers’ (only available in German), (Cologne, 1968).