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it seems that there are so many variability in attribution of nomencl,ature for veins and cells, hence the difficulty.
But I wonder what is the basic rule for split these examples:
R1, R2, R3
R1, R2+3, R4+5
R1+2, R3+4

When the R1 turns R1+2?
To know whcih books/artciles are clear about this issue would be great. Thank you.