1537
Since February 2014 , a major patent related to SLS expired ( Apparatus for producing parts by selective sintering n.d. ) .
 concept or principle: patent; manufacturing process: SLS; manufacturing process: selective sintering
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: 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:
 concept or principle: patent; manufacturing process: SLS; manufacturing process: selective sintering