Sentence:  Hence , when the address * * f is computed from * * f , the cell * * f and all Y-cells in its chain must be inspected to determine whether * * f is already in the form <WSD>list</WSD> or whether it should be added to the form list and the chain . 
Meaning of the word marked with <WSD> tags:  a database containing an ordered array of items (names or topics)