When Was Close-Coupled Canards First Possible?
While I know a delta-winged aircraft's takeoff and landing performance can be improved by using a canard to shift the C/L forward allowing the elevons to be drooped; some aircraft use close-coupled canards to further improve low speed performance by using the vortices generated off the tips of the canard to amplify the vortices off the delta-wing.
When did the knowledge first exist to produce a canarded delta whereby the vortex off the canard could be used to amplify the vortex off the wing's leading-edge?