Table 3: Number of maser sources in the sample depending on the presence (+) and absence (-) of four OH transitions.

1612		+	+	+	-	-	-	-
1665		-	+	+	+	+	-	+
1667		-	-	+	-	+	+	+
1720		-	-	-	-	-	-	+
Frequency		1	3	1	11	32	1	6
(MHz)		Number of sources