1V voltage reference and temperature coefficient
There are two questions:

1) About diodes and temperature coefficient: the p-n junction in conduction state has voltage drop about 0.5V...0.8V, and - what is interesting, temperature coefficient of this drop is near constant and equal -2.2mV/K (without valuable dependency on current and voltage drop). This -2.2mV/K coefficient is the result of some physical properties of junctions based on silicon. So, this coefficient is very frequently used for compensation of temperature drift, because it is well defined.

2) About drift of 1V reference voltage: it depends on type of IC, used as reference: each IC type has own temperature coefficient - you can find this in reference data of this IC. For example, LM385 is very well compensated in temperatures about room temperature (25 Celsjus degrees), and - in typical applications - don't need additional compensation. If you need better compensation, there is no universal rule for all cases. You need always start with checking manufacturer's recomendations, very often placed in application notes. For example, TI in his datasheet shows precision 10V source built on LM385 (Fig. 17 in http://www.ti.com/lit/ds/symlink/lm285-adj.pdf).