It also hired Citigroup and Morgan Stanley to explore refinancing or restructuring of $ 175 million in senior notes due next year .
ATA also has hired Citigroup and Morgan Stanley to evaluate options for refinancing or restructuring $ 175 million of 10.5 percent senior notes due in August 2004 .
hierarchical arrangement of criteria that predict a classification or value  easy to understand easy to implement can deal with partial or incomplete data