How far do the sources agree with each other?
How and why do they disagree?
How similar are the two sources?
Is one useful/not useful? Why?
who, what, how, when
biased? - still could be useful reliable provenance
Is a source reliable/not reliable? Why?
Do you believe somebody? Which source can be trusted more?
How much do the sources prove a view that…?
Do the sources support the view that…?