Steve, yep, it's in the LTZ100 thread. We discussed intensively the sense or nonsense of those slots in the Datron PCB design, which is very often (blindly) copied by others... Mickle T. contributed the already known schematics and he measured all resistor values of the Vishay array. Then, quarks simply added a schematic of this array, which he received directly from Vishay, obviously. So, Datron used 21 Ohm in series with the Zener for better T.C. (originally 50ppm/K), 9k/659 as initial divider for temperature regulation (altered by the external temp. PWM), 128 Ohm for the Zener current, 39k as collector resistor for the reference transistor. There's no complete schematic yet, but now it's possible to finalize that. Here's the link: http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/300/ Frank