Question about elements order

[F.schettino]

I use 3 groups of elements in a form.

I had no problems to order elements in each group, but I don't understand how order them in the corresponding list, so in the list the order is not as I need.

E.g., I ordered in each group:
Group A: elementA1, elementA2, ... elementAn
Group B: elementB1, elementB2, ... elementBn
Group C: elementC1, elementC2, ... elementCn

In the form, all is ok; in the list I have, e.g.:
elementC3, elementB2, elementA1, elementC1, elementB1,...
so they are not ordered with some rule.

I would expect:
elementA1, elementA2, ... elementAn, elementB1, elementB2, ... elementBn, elementC1, elementC2, ... elementCn

Someone can help me?
Thanks.