Cereoid-XXXXX schreef
You neither give the name of the book (if it even exists)

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If you are in such a need of a book, maybe you should buy one every so
often. It can be very educational.
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Selection of cultivars does not need to be from interspecific hybrids.

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Maybe you should consult the archives of the list. This was covered pretty
extensively a while back
PvR