Bibliography
- Harris , Jacqueline . “Plants: Barometers of Pollution,” . Current Science , 60 3 – 4 .
- Houston , Walter S. “Lichen Survey to Underscore Nation's Pollution Problems,” . Current Science , 60 6 – 12 .
- Marteka , Vincent . “Current Science Lichen Survey,” . Teacher's Edition of Current Science , 60 26
- Stranix , Edward . “The Cemetery: An Outdoor Classroom,” . Teacher , 93 ( 2 ) 66 – 67 .