They require a constant source of cool, clean water.
The iron oxide process requires an efficient source of heat.
Such an increase requires an external source of energy.
Human studies required a better source of the radioactive Iodine.
They do not generally require a source of water other than food, but will use it given the opportunity.
Power required a source, and someone to control it.
To bring over any substantial numbers in the future would certainly require a source of grant funding.
For its missiles to be effective, China would require a source of data about possible targets.
Guided missiles require a source of electrical power during flight.
However, this requires a bright and highly monochromatic light source to be effective.