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In , the contour offset method and the structural skeleton based method , including a support structure constraint , were investigated .
 enabling technology: contour offset method; engineering feature: structural skeleton; engineering feature: support structure
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:
 enabling technology: contour offset method; engineering feature: structural skeleton; engineering feature: support structure