I like to use ```ZU.xpath``` and then a ```for``` loop as here:
https://github.com/zotero/translators/blob/master/CLACSO.js#L202
(I believe technically for loops are slightly less efficient, but that doesn't matter with the small number of iterations here and I find this easier to read)
but you can also do this with ```while``` and ```doc.evaluate``` such as here:
https://github.com/zotero/translators/blob/master/Optical%20Society%20of%20America.js#L53