1. Preparing egg yolk color standards;Ashton;Canadian Paint and Varnish,1961
2. Official Methods of Analysis;Association of Official Agricultural Chemists,1960
3. Producing dark colored egg yolks;Carlson;South Dakota Farm and Home Res.,1961
4. The yolk color index;Heiman;U.S. Egg Poultry Mag.,1935
5. Color in Business, Science and Industry;Judd,1952