Citrus Fruit Juice Equivalencies?

This is from my old Better Homes & Gardens cookbook.
juice of 1 lemon= 3-4 Tablespoons

juice of 1 orange = 6-7 Tablespoons
(Doesn't list lime juice.)
I don't always have fresh lemons or oranges to squeeze so I keep a bottle of lemon juice handy & use it. If the recipe calls for juice of 1 lemon, I use 3-4 Tablespoons of the bottled juice instead. I do the same with orange juice.