（一）Autoencoders and Sparsity章节公式错误：
s2 应为 s3。
意为从第2层（隐藏层）i节点到输出层j节点的误差加权和。
（二）Support functions for loading MNIST in Matlab文件名错误
% Change the filenames if you've saved the files under different names
% On some platforms, the files might be saved as
% train-images.idx3-ubyte / train-labels.idx1-ubyte
images = loadMNISTImages('train-images-idx3-ubyte');
labels = loadMNISTLabels('train-labels-idx1-ubyte'); % We are using display_network from the autoencoder code
display_network(images(:,:)); % Show the first images
disp(labels(:));
应为
images = loadMNISTImages('train-images.idx3-ubyte');
labels = loadMNISTLabels('train-labels.idx1-ubyte');