How to build a request to the Yandex.Metrica API comparing two months and selecting sources and search engines?

Question

Yandex

Hello. You need to build a request to the new version of the Ya.Metrika API. You need to get the following: attendance, comparison of two months, grouped by sources (All sources together, Yandex, Google, direct visits, clicks on links on sites), displaying data in numerical terms and, if possible, in percentage terms of the total number visits. I'm trying to do it like this:
api-metrika.yandex.ru/stat/v1/data/comparison?metrics=ym:s:users&dimensions=ym:s:<attribution>trafficSource,ym:s:<attribution>SourceEngine&date1_a=2014- 07-01&date2_a=2014-08-01&date1_b=2014-09-01&date2_b=2014-10-01&ids=<counter_id>
In this query, I can not discard unnecessary data - clicks on links on sites are not shown entirely from all sites, but broken down by individual sites. And the row_ids parameter does not work here if it is substituted. Help me please)