'The mystery of the wooden legs' originally published: 1964.
'Seven white pebbles' originally published: 1960.
OBNB doesn't sell books, but you may be able to find a copy at one of these websites:
The mystery of the wooden legs / [by] Griselda Gifford ; illustrated by Barry Wilkinson ; &, Seven white pebbles / [by] Helen Clare ; illustrated by Cynthia Abbott by Griselda Gifford. ISBN 0370110005. Published by Bodley Head in 1975. Publication and catalogue information, links to buy online and reader comments.
![The mystery of the wooden legs / [by] Griselda Gifford ; illustrated by Barry Wilkinson ; &, Seven white pebbles / [by] Helen Clare ; illustrated by Cynthia Abbott](http://ecx.images-amazon.com/images/I/51OdgRpGk6L._SL160_.jpg)