'former studies have' is a correct and usable phrase in written English.
It can be used to refer to studies that have been conducted previously. For example: "Former studies have shown that playing music can help improve memory."
Former studies have demonstrated its anti-inflammatory and anti-cancer activity.
Former studies have been focused on changes in physical and mechanical properties of soil due to freeze thaw cycles.
Former studies have implied that the proliferation, survival, migration and drug resistance of MM cells are in association with the activation of several signaling pathways.
Former studies have reported exosome as a transporter of diverse molecules associated with drug-resistance and metastasis in cancer13,14,15.
Former studies have pointed out that a simple modification of the design of slow strain rate tensile specimens was particularly convenient for evaluating the susceptibility to intergranular stress corrosion cracking of nickel-base alloys.
Former studies have pointed out that even if intergranular oxidation still occurred, intergranular crack initiation was inhibited due to specific mechanical loadings which were identified as Portevin-Le Châtelier (PLC) plastic instabilities.
Former studies have reported a positive relationship between openness and inward FDI.
However, this question still holds since former studies have limited power.
Some former studies have provided justifications for designing flexible pavement structures with higher strength than what is typically recommended by some current design methods [1, 2].
Former studies have also been showed that a very few statistical methods such as Weibull and Rayleigh distribution models can also be equally used (Akpinar and Akpinar 2005).
