Poorly correlated materials and the factor

The purpose of the present section is to review the questions why is it there and what is its magnitude The most important thing to grasp, however, is that the term it enters is a very small term for practical purposes, uncertainty about where / lies between 1 and 0 is of no consequence at all compared with other uncertainties. 

Fortunately, as discussed on page 125, there seem to be good reasons for expecting d r Jdx to be small compared with d a Jdx in all situations to which this book refers. Hence as long as / is close to zero, we do not need to face the difliculty of establishing exactly what its magnitude is. 

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