conjectures that every bridgeless graph has a nowhere-zero 5-flow and every bridgeless graph without the Petersen graph as a minor has a nowhere-zero 4-flow
The Structure of Fields, David J. Winter, (1974, ISBN 978-3-540-90074-0) Random Processes, Murray Rosenblatt, (1974, ISBN 978-0-387-90085-8) Measure Theory