Helen Philbrick (1910-2011) worked with Richard Gregg and Evelyn Speiden Gregg to experiment with companion planting in the Gregg's own garden. She wrote extensively on the subject. Richard Gregg was an early pioneer of companion planting. In the 1940s, he and Evelyn Speiden Gregg used their own garden to experiment with different plants.
'The first version of this book came out as early as 1943 and is
based on the observation that certain plants seem to affect others
growing near them in both a favourable and unfavourable manner.
This knowledge can enable us to improve the quality of our food and
flowers and reduce losses due to pests and disease. [...] Readers
will be able to test and
confirm the suggestions for themselves. '
-- Network Review