There is a book I have had for many years. It's called Stretching, by Bob Anderson. It is similar to the one at the left, Getting Back in Shape. I don't know how to use this new Blogger set-up, or I would insert a photo of it (I really, really dislike the new Blogger!!!). Anyway, I highly recommend Stretching.
My favorite one is to sit on the floor or your bed, bring the soles of your feet together, then GENTLY bend forward at your hips. Do not bend at the waist or round your back. Go only so far as is comfortable, with a SLIGHT stretching feeling. Hold for 30 seconds or until you can feel just a bit less tight. Then, move just a bit more forward and hold for 20 seconds. When moving forward, pretend there is a string attached to your chest, pulling you forward. It feels wonderful in your hips and lower back.