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In this paper , functionally gradient materials ( FGM ) with composition variation from a copper alloy to a soda-lime glass were manufactured using a proprietary nozzle-based multi-material selective laser melting ( MMSLM ) system .
 functionally gradient materials, FGM, composition, copper alloy, soda-lime glass, manufactured, multi-material selective laser melting, MMSLM
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 functionally gradient materials, FGM, composition, copper alloy, soda-lime glass, manufactured, multi-material selective laser melting, MMSLM