Sentence:  If * * f leads to an address * * f that is equal to the address computed from * * f , even though * * f does not match * * f , the chain of information cells is extended from * * f by storing the address of the next <WSD>available</WSD> cell in the Y-region , * * f , in * * f . 
Meaning of the word marked with <WSD> tags:  obtainable or accessible and ready for use or service