Available on Project MUSE and JSTOR. Online access to Contemporary Literature is available as part of the Project MUSE collections. All back issues of Contemporary Literature beginning with Vol. 1, 1960 are available online through the JSTOR digital archive.
Many manufacturers recommend water heater anode replacement every two to four years depending on the hardness of the water that passes through the tank and the quality of the water heater lining.
Replace the 20 year old water heater. It's past its life span. They now make more energy effecient water heaters which will lower your utility bill. Put a blanket around the new water heater while you're at it.