There is no simple quantification of the meaning of ‘insubstantial part’. We cannot simply claim that x% of the work is an insubstantial part. However there are a few useful guidelines:

If the reproduction of the copyrighted content makes it unecessary to view or purchase the original work, then that is clearly more than an ‘insubstantial part’.

If we are making a copy for the purposes of criticism or review, then we should only use content that is necessary to support the argument that we are making. Edit carefully. Be efficient. For more help, talk to Clayton Jones (University Legal Compliance Officer).