Russian ⇄ English +

как это часто случается stresses
gen.	as (they) very often (are; If the natural drives are insufficient, as they very often are, then the pressure can be artificially maintained by injecting water into the aquifer or gas into the gas cap. ArcticFox)
math.	as is often the case; as often happens
как это часто случалось
fig.of.sp.	as was often the case (sophistt)