Official reference for Google Spreadsheet Api Stru

Question

I'm looking for the official reference for the query syntax used for creating structured queries for requesting rows in the Google Spreadsheet API, as discussed here

The only example given is:

 GET https://spreadsheets.google.com/feeds/list/key/worksheetId/private/full?sq=age>25%20and%20height<175

There must be some references of the query syntax used somewhere?

In particular I want to know how to query for all rows (containing column a and b) for which val(a) != val(b)