List at least three different tactics used by the vietcong in their fight against u. s. forces.

One tactic was using b.ooby traps

They would dig holes in the ground which would be covered by leaves and branches under which they'd put sharp objects like metal pikes or sharpened bamboo or similar things and US forces who wouldn't know this would fall into the holes and get punctured severely. They would also put traps on trees which would be activated through a trip wire or through similar mechanisms

Another was digging hidden tunnels in the ground. 

They dug out small tunnels underground which would be knowable just to them and they would be able to traverse large areas with ease and ambush people or run away and hide or flank people or similar things. If US troops found the tunnels they would just get lost in them because there were so many that it was like a maze.

One tactic was avoiding battle completely

They would never attack outright but would wait in ambushes for enemies to fall into their trap and would then attack quickly, kill a few soldiers, and retreat instantly and hide. They would never fight in the open for longer periods of times and would retreat as soon as they achieved something. This guerrilla warfare was common for them.

What book is this referring to?