I spent around a decade as a dedicated professional in the area of second-language acquisition of adults.

I haven't read through this in its entirety yet (I'm cooking dinner). I'll go ahead a post this to keep the thread warm.

At first glance it seems to be very comprehensive. In my experience having relied on many of these approaches and observations has been the primary fulcrum of successful acquisition. although some specific conclusions i must reject outright, for now; that SLA is slowed by speaking the target language rings of absolute blasphemy.