How to make an app_config.xml to limit CPU threads used by multi-threaded applications in BOINC

This is a quick and simple guide on how to tell multi-threaded work units in BOINC to use a limited number of pre-determined CPU threads.
UA-cam doesn't allowed angled brackets in descriptions. Replace each [ and ] with the left angle (shift + comma) or the right angle (shift + period)
[app_config]
[app]
[name]ATLAS[/name]
[max_concurrent]1[/max_concurrent]
[/app]
[app_version]
[app_name]ATLAS[/app_name]
[plan_class]vbox64_mt_mcore_atlas[/plan_class]
[avg_ncpus]1.0[/avg_ncpus]
[cmdline]--nthreads 1 --memory_size_mb 4800[/cmdline]
[/app_version]
[/app_config]