"indicate source" is correct and can be used in written English.
You can use it when you are asking someone to provide information about the origin of a particular statement or idea. For example, "Can you please indicate source of this data?".
'S' and 'D' indicate source and drain electrodes, respectively.
They indicate source organic matter and distinguish between allochthonous terrestrial organic matter and autochthonous organic matter.
Orange circles indicate source locations and amplitudes of other eruption tremor episodes listed in Table 1.
A yellow star and a red triangle indicate source and receiver, respectively.
Yellow shaded regions indicate source areas of past and anticipated megathrust earthquakes (Headquarters for Earthquake Research Promotion [2001]; Nakamura [2009]; Goto [2013]).
A destination node finds this from route request message it receives in which first 96 bits indicate source, destination identity, and QoS measure information whereas remaining bits contain list of nodes' IP addresses through which request message has traveled.
They have been more careful to qualify speculation, indicate sources and to avoid clumsy phrases such as 'Muslim terrorists'.
Solid and hollow markers indicate sources of vector and pseudo-scalar data, respectively.
Entries marked * indicate sources that produce correlated photon pairs that are not entangled in polarisation.
Literature references in the rightmost column of Table 1 indicate sources of the information contained in the corresponding requirement.
It would be desirable if authors clearly indicate sources of ribosomes, factors and tRNA for every experiment.
