Previous link to the Tensorflow 1 Detection Model Zoo, https://github.com/tensorflow/models/blob/master/research/object_detection/g3doc/detection_model_zoo.md, leads to a page that didn't exist anymore (Error 404). 
The new link to the Tensorflow 1 Detection Model Zoo should be: https://github.com/tensorflow/models/blob/master/research/object_detection/g3doc/tf1_detection_zoo.md.