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Busulfan levels were measured by a gas chromatographic - mass spectrometry assay in the plasma and cerebrospinal fluid of 9 children without central nervous system disease under 600 mg / m2 busulfan with clonazepam : busulfan cerebrospinal fluid : plasma ratio was 1 . 39 .
 Chemical: Busulfan; Disease: central nervous system disease; Chemical: busulfan; Chemical: clonazepam; Chemical: busulfan
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 Chemical: Busulfan; Disease: central nervous system disease; Chemical: busulfan; Chemical: clonazepam; Chemical: busulfan