1 “... volume, as well as references to papers in which such solutions have been published...”

2 “... volume, as well as references to papers in which such solutions have been published...”

3 “... of the problems raised in the previous volume, as well as references to papers in which such solutions have been...”

4 “... of the problems raised in the previous volume, as well as references to papers in which such solutions have been...”

5 “... of the problems raised in previous volumes, as well as references to papers in which such solutions have been...”

6 “... of the problems raised in previous volumes, as well as references to papers in which such solutions have been...”