4067
Furthermore , the BLM was combined with the toxic equivalency factor approach in predicting toxicity of mixtures of Cu ( 2 + ) - Zn ( 2 + ) and Cu ( 2 + ) - Ag ( + ) .
 Cu ( 2 + ) - Zn ( 2 + ), Cu ( 2 + ) - Ag ( + )
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Cu ( 2 + ) - Zn ( 2 + ), Cu ( 2 + ) - Ag ( + )