nested_lmer <- function(x, remove=0) {

# Design specification: mtc nested within levels of cv  
x$design <- factor(paste(x$cv, x$mtc, sep=""))
x$design <- C(x$design, matrix(c(-.5, +.5,   0,   0,  # (1)  mtc | cv=1 - invalid
	                               0,   0, -.5, +.5,  # (2)  mtc | cv=2  - valid
	                             -.5, -.5, +.5, +.5   # (3)  cv  
	                                  ), 4, 3), 3)  

# Remove subjects with zero-entry design cells if requested
if (remove) {
	x.n <- table(x$ID, x$design) 
	temp <- vector()
	for (i in 1:dim(x.n)[1]) {
		temp[i] <- any(x.n[i,]==0)
	}

	vid <- attr(x.n, "dimnames")[[1]][temp]  # vid contains ids with 0
	v <- vector()
	for (i in length(vid) ) {
		temp <- which(x$ID == vid[i])
		v <- c(v, temp)                      # v contains records of ids
	}
	if(length(v) > 0) {x <- x[-v, ]}
}

print(table(x$ID, x$design)) 

m <- (lmer(rt ~ design + (1|ID), x ))
m
}