@article{GDZPPN002228432, title = {Counterexamples for unique continuation.}, journal = {Manuscripta mathematica}, volume = {61}, year = {1988}, pages = {21-48}, zbl = {0653.30013}, url = {http://dml.mathdoc.fr/item/GDZPPN002228432} }
Martio, Olli. Counterexamples for unique continuation.. Manuscripta mathematica, Tome 61 (1988) pp. 21-48. http://gdmltest.u-ga.fr/item/GDZPPN002228432/