Two liberos - questions

[PaREF]

Well, I was line judge at two D-1 mens' volleyball matches the past two evenings. The home team used two liberos (both nights) and one of the visiting teams used two liberos. They used the liberos in a manner that I suspected for which the rule was instituted.

The starting libero replaced the two middles. The second libero replaced an outside hitter (back row, of course) when the starting libero went out and the middles served. The starting libero came back in and the second libero came back out when the middle lost his serve. So there was always a libero on the court. So, there were two libero replacements simultaneously (L1 replaced by middle and OH2 replaced by L2 then after MH ends his term of service, MH replaced by L1 and L2 replaced by OH2).

We also had one instance where L1 was replaced by L2 (in my second match).

Visiting team in match two questioned whether a libero could replace a libero. R1 and R2 were National referees and said it was OK.