{TAIL ~ A model} of the subtree depicts the maximum and minimum delays of the clock signals rising and falling edges between the subtree root and {HEAD ~ the sinks} within the macro cell as functions of the clock signals rising and falling edge transition times as they arrives at the subtree root and also as functions of the relative amount of delay the rising and falling edges experience as they pass from the clock tree root to the subtree root 
{ TAIL ~ A model } of the subtree depicts the maximum and minimum delays of the clock signals rising and falling edges between the subtree root and { HEAD ~ the sinks } within the macro cell as functions of the clock signals rising and falling edge transition times as they arrives at the subtree root and also as functions of the relative amount of delay the rising and falling edges experience as they pass from the clock tree root to the subtree root
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