queries to timeseries are restrictable with "=" for all fields
e.g.
https://toar-data.fz-juelich.de/api/v2/timeseries/?var_id=19&sampling_frequency=Hourly
delivers all hourly time series of variable pm2p5 (AND).
Filtering should also work for lists, e. g.
https://toar-data.fz-juelich.de/api/v2/stationmeta/?var_id=19,7
delivers all time series of variable pm2p5 OR toluene.
This should also work in combination with #103 (closed) .