Show select canvases

Two pages from the Mac Durnan Gospels shown by setting restricttolabels to "19,12".

Notes

The choice of labels as reference points was done primarily because labels are generally easy to identify by the general user (Mirador reveals them), make more sense than index numbers and are arguably more reliable than index numbers (e.g. the provider may wish to insert an image of the spine at some point, incrementing subsequent canvases by one).

There is a trade-off, however. Labels may change, too, and so in the interest of long-term support, it makes sense to rely on canvas IDs instead (see Lab/Mirador/CanvasNotifier for one way of retrieving IDs). A further reason for doing so is that labels are not guaranteed to be unique, as seen on the Internet Archive/IIIFLab, which may use blanket labels.