Thus some previous work turned to investigate its surrounding contexts' polarities (such as the sentences before or after s), and then assigned the majority polarity to the collocation c (Hatzivassiloglou and McKeown, 1997;Hu and Liu, 2004;Kanayama and Nasukawa, 2006).
since the amount of contexts from the original review is very limited, the final resulting polarity for the collocation c is insufficient to be reliable.