[R] grouping for lme with nested repeated measurements

[Nicolaas Busscher]

I am using lme to handle repeated measurements.
So far i can follow the examples from the book from pinheiro and bates.
Now i get the problem , that i have "nested" repeated measuremnts, and i cant find out how to do the grouping part of the lme formula.

1.The simple problem ist that i have different Samples , from which i make repeated measurements (each sample is measured 6 times) and i repeat this experiment over several Days, so i get the lme grouping term "random=~1|Days/Sample".

2. Now i am measuring with 2 different measuring Apparatus the same Sample each 6 times, to see how big the difference from the appratus is. 
Because Apparatus is on the level of repeated measurements i cant write Days/Sample/Apparatus. the lme function offers a list() feature to design the grouping, but i didnt understand this, if it is the solution to the problem.

Maybe somebody had the same Problem?
best greetings
N.Busscher
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