Lophophora
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Here is a free download for you! An article written by an Australian guy on grafting cacti (23 pages with lots of photos). He deals with grafting Lophophora but the techniques apply to any cacti.
This is an Adobe pdf document. You will need Adobe Reader to open it - obtainable FREE here.
Teo's Small Book of Grafting Cacti
Teo Nanacatyl
Download this for FREE here