Task: Pos Tagging
Input (English): Sentence: In attempting to improve specificity of staining , the fluorescein-labeled antisera used in both direct and indirect methods were treated in one of several ways : ( {{ 1 }} ) They were passed through Dowex-2-chloride twice and treated with acetone insoluble powders ( Coons , 1958 ) prepared from mouse liver or from healthy sweet clover stems or crown gall tissue produced by Agrobacterium tumefaciens ( E. F. Smith & Townsend ) on sweet clover stems . 
Word: 1
Output (English): NUM