In order to complete this task, you need to review each of the sonnets in question and see if you can determine the one most important line or sentence of each one. THAT would be the evidence that Shakespeare does in fact express his themes in a clear and precise way. Sonnets 18 and 60 talk about the lasting power of poetry; Sonnets 29 and 30 both speak of the power of memory in making the speaker feel better, especially as he remembers the person to whom the sonnets are addressed. Sonnets 73 and 116 are both about love and the power of love to endure. Look to each of the sonnets and decide for yourself which seems to more clearly capture that theme and then look to see which other lines support that theme. It is by looking at the theme sentence (frequently found in the final couplet) and then looking at the other poetic devices he uses earlier in the poem that Shakespeare's meaning becomes clear.