Is it possible to use superposition code for more than two users?

Superposition coding is used to transmit the data of users simultaneously on the same channel. On reception however, each user 'j' is able to remove interference from the users having weaker channel gains as compared to user j. I want to know if it is possible to transmit the data of more than two users, simultaneously, using superposition coding?

I believe that MIMO techniques use superposition to encode multiple channels. see this Wikipedia article.
https://en.wikipedia.org/wiki/MIMOThe difficulty of  decoding the correct data will increase as the number of users increases so there will be a practical limit.

To extend Elizabeth Simon's comment, there are many examples of the use of superposition to encode multiple channels (with many terminologies): code-division-multiplex spread spectrum, orthogonal-frequency-division multiplex (OFDM), frequency-hopping spread spectrum. Good old AM broadcast radio is an example of frequency-division multiplexing: the stations are on different frequencies in a common broadcast band. The mathematical idea, is to have a set of functions whose autocorrelations are large but whose cross-correlations are zero. Sinewaves and cosinewaves of various frequencies are the most well-known set, and the calculation is the Fourier series or Fourier transform. Ultrawideband radio (also known as impulse radio) uses impulses occurring at different times.Monaural analog FM broadcast radio is an unusual case: The wideband broadcast FM signal occupies more bandwidth that the bandwidth of the audio being transmitted, so FM is an example of spread-spectrum, even though FM is not digital and not encrypted. The FM signal has poor cross-correlation with impulses such as static, so FM receivers are able to reject static that AM receivers cannot. Thanks, Edwin H. Armstrong!