The following information accompanied stocks donated to the Bloomington Stock Center by Thom Kaufman, Indiana University.
In P{lab-GAL4.DR}, a 7.6 kb EcoRI fragment from the intron of lab drives strong, early GAL4 expression in the dorsal ridge of the embryonic labial segment.  The enhancer fragment is depicted in figure 7 of Chouinard and Kaufman, 1991 (http://flybase.org/reports/FBrf0053767.html) and the GAL4 expression of this construct recapitulates the expression of a similar lacZ construct (P{7.6labHZ})  in the paper.  Amy Kalkbrenner constructed P{lab-GAL4.DR} using the transformation vector pP{GawB}. 
P{lab-GAL4.DR}D2 is a homozygous and hemizygous viable and fertile, X chromosome insertion.  In addition to dorsal ridge expression, GAL4 is expressed in the salivary glands.  Spotty, ectopic head expression is also seen.
P{lab-GAL4.DR}H1 is a homozygous viable and fertile, second chromosome insertion. In addition to dorsal ridge expression, GAL4 is expressed in the salivary glands and late frontal sac and in stripes in the late ectoderm.  Ectopic head expression is also seen.